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An Introduction to Behavioural Ecology

Vörumerki: John Wiley
Vörunúmer: 9781118399446
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An Introduction to Behavioural Ecology

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  • Front Matter
    • COMPANION WEBSITE
    • Contents
      • COMPANION WEBSITE
    • Preface
    • Acknowledgements
  • CHAPTER 1 Natural Selection, Ecology and Behaviour
    • Watching and wondering
      • Fig. 1.1 A foraging starling. Photo © iStockphoto.com/Dmitry Maslov
      • Tinbergen’s four ‘why’ questions
      • Reproductive behaviour in lions
        • Fig. 1.2 (a) A lion pride. (i) The females are returning to the middle of their territory after chasing away a neighbouring pride. (ii) Females and cub. (iii) Males patrolling the territory and (iv) relaxing. (v) Male with cub. Photos © Craig Packer (b) Infanticide: a male that has just taken over ownership of a pride, with a cub in his jaws that he has killed. Photo © Tim Caro
        • Table 1.1 Summary of causal and functional explanations for two aspects of reproductive behaviour in lions (Bertram, 1975; Packer and Pusey, 1983a, 1983b).
    • Natural selection
    • Genes and behaviour
      • Drosophila and honeybees: foraging, learning and singing
      • MC1R: mate choice and camouflage
      • Blackcaps: migratory behaviour
        • Fig. 1.3 Blackcap migration. (a) Male blackcap with nestlings. Photo © W. B. Carr (b) Migratory restlessness (measured in cages) during the time of autumn migration in blackcaps from Germany, the Canary Islands and F1 hybrids of these two populations. From Berthold and Querner (1981). Reprinted with permission from AAAS. (c) Artificial selection in aviary populations for higher (red) and lower (blue) migratory behaviour in a partially migratory blackcap population from southern France; A: frequency of migrant individuals; B: migratory activity in migrants. From Berthold et al. (1990) and Pulido et al. (1996). (d) Traditionally, in autumn blackcaps from southern Germany migrate in a south-west direction to winter in the western Mediterranean region. During the past 40 years a new migration habit has evolved, with some blackcaps migrating west to Britain; F1 offspring from these adults inherit the new direction. Each point in the circles to the left refer to the direction of migration of one caged individual and the arrows indicate the mean direction). From Berthold et al. (1992). Reprinted with permission from the Nature Publishing Group.
    • Selfish individuals or group advantage?
      • Theoretical considerations
        • Fig. 1.4 Wynne-Edwards’ model of group selection. Groups of selfish individuals (S) over-exploit their resources and so die out. Groups of altruistic individuals (A), who do not over-exploit resources (e.g. by having fewer offspring than they could potentially raise) survive.
      • Empirical studies: optimal clutch size
        • Fig. 1.5 (a) (i) Wytham Woods, Oxford, the site of a long-term study of great tit reproductive behaviour. Photo © Jane Carpenter (ii) A nest box. Photo © Ben Sheldon. (iii) Female great tit incubating a clutch. Photo © Sandra Bouwhuis (b) Bars: The frequency distribution of the clutch size of great tits in Wytham Woods. Most pairs lay 8–9 eggs. Curve and blue dots: Experimental manipulation of brood size shows that the clutch size that maximizes the number of surviving young per brood is slightly larger than the average observed clutch size. From Perrins (1965).
        • Fig. 1.6 Experimental manipulation of brood sizes in great tits. (a) In larger broods of great tits the young weigh less at fledging because the parents cannot feed them so efficiently. (b) The weight of a nestling at fledging determines its chances of survival; heavier chicks survive better. From Perrins (1965).
        • Fig. 1.7 The influence of adult mortality on the optimal clutch size. The number of young produced versus clutch size follows a curve, as in Fig. 1.5, with b1 being the clutch size which maximizes the number of young produced per brood. Increased clutch size, however, has the cost of increased adult mortality, shown here for simplicity as a straight line. The clutch size which maximizes lifetime reproductive success is b2, where the distance between the benefit and cost curves is a maximum. This is less than the clutch size b1, which maximizes reproductive success per brood. From Charnov and Krebs (1974).
        • Fig. 1.8 Fitness of female great tits in the experiment of Visser and Lessells (2001). Fitness was measured as (female survival to next breeding season) + (0.5 × number of offspring surviving to next breeding season). The logic behind this measure is that each offspring has only half the female’s genes, so has half the ‘genetic value’ of the female herself. Female fitness is measured relative to controls (who raised the clutch size they initially laid) for three experimental groups who each had two extra chicks to raise, but with varying extra costs (see text). Females given free chicks or free eggs did better than controls but females forced to pay the full costs of laying and incubation had lower fitness than controls. From Visser and Lessells (2001).
        • BOX 1.1 THE OPTIMAL TRADE-OFF BETWEEN SURVIVAL AND REPRODUCTIVE EFFORT (PIANKA AND PARKER, 1975; BELL, 1980)
          • Fig. B1.1.1
        • Fig. 1.9 Experiments on clutch size in magpies. Pairs that had initially laid 5, 6, 7 or 8 eggs were given experimentally reduced or enlarged broods. Pairs that had naturally laid large clutches did better with large broods and those naturally laying small clutches did better with small broods. From Högstedt (1980). Reprinted with permission from AAAS.
    • Phenotypic plasticity: climate change and breeding times
      • Fig. 1.10 Phenotypic plasticity in laying dates in response to spring temperatures. Dashed lines represent examples of reaction norms for different individual females, who may differ in their average laying date (elevation) or in their plasticity in response to spring temperatures (slope). In Wytham Woods, UK, the great tits respond as in (a), with no significant variation between females in plasticity and a strong average population response to temperature (solid line). In the Hoge Veluwe, The Netherlands, the great tits respond as in (b), with no significant average population response (solid line) but significant variation in individual female plasticity. After Charmantier et al. (2008). Reprinted with permission from AAAS.
      • Fig. 1.11 (a) In Wytham Woods, UK, the mean laying date of great tits has become earlier, especially since the mid 1970s. (b) Spring temperatures have also increased, as measured by ‘Warmth Sum’, which is the sum of daily maximum temperatures between 1 March and 25 April (the pre-laying period). The rates of change in mean egg laying date with temperature (c) and caterpillar emergence with temperature (d) are similar. (e) Phenotypic plasticity in response of individual female great tits, measured as their difference in laying date in successive years plotted against the difference in spring warmth in the same pair of years. Figures a-e from Charmantier et al (2008). Reprinted with permission from AAAS. (f) Female great tit. Photo © Thor Veen. (g) Winter moth caterpillar on oak. Photo © Jane Carpenter.
    • Behaviour, ecology and evolution
    • Summary
    • Further reading
      • Topics for Discussion
  • CHAPTER 2 Testing Hypotheses in Behavioural Ecology
    • The comparative approach
    • Breeding behaviour of gulls in relation to predation risk
      • Fig. 2.1 (a) The black-headed gull nests on the ground. Photo © osf.co.uk. All rights reserved. (b) The kittiwake nests on tiny ledges on steep cliffs. Photo © iStockphoto.com/Liz Leyden.
      • Table 2.1 Comparison of breeding traits of two gulls: the ground-nesting black-headed gull Larus ridibundus and the cliff-nesting kittiwake Rissa tridactyla (Cullen, 1957).
    • Social organization of weaver birds
      • Fig. 2.2 Differences in social organization in weaver birds. (a) Red-headed weaver Anaplectes melanotis; a woodland insectivore which often breeds in monogamous pairs on dispersed territories. (b) Southern masked weaver Ploceus vellatus; a savannah seed-eater which nests in colonies and is polygynous. (c) Village weaver Ploceus cucullatus, another colonial, polygynous savannah species. All photos © Warwick Tarboton.
      • Table 2.2 Social organization of weaver bird species (Ploceinae) in relation to habitat and diet (Crook, 1964; Lack, 1968).
    • Social organization in African ungulates
      • Fig. 2.3 Differences in social organization of African ungulates. (a) Kirk’s dik-dik Madoqua kirki live in pairs in woodland. Photo © Oliver Krüger. (b) Impala live in small groups in open woodland and grassland. Photo © Bruce Lyon. (c) Wildebeest graze in huge herds out on the open plains. Photo © iStockphoto.com/William Davies.
      • Table 2.3 The social organization of African ungulates in relation to their ecology (Jarman, 1974).
    • Limitations of early comparative studies
      • Summary
    • Comparative approach to primate ecology and behaviour
      • Fig. 2.4 Differences in social organization in primates. (a) A solitary insectivorous tarsier. Photo © iStockphoto.com/ Holger Mette. (b) A small group of black and white colobus monkeys, which eat leaves in the forest. Photo © iStockphoto.com/ Henk Bentlage. (c) A large group of gelada baboons, which feed on the ground on grass leaves and roots. Photo © iStockphoto.com/ Guenter Guni.
      • Home range size
        • Fig. 2.5 Home range size plotted against the weight of the group that inhabits the home range for different genera of primates. The solid circles are folivores, through which there is a solid regression line. The open circles are specialist feeders (insectivores or frugivores) and the regression line through these points is dashed. Some of the genera are indicated by name. From Clutton-Brock and Harvey (1977).
      • Sexual dimorphism in body weight
        • Fig. 2.6 The degree of sexual dimorphism increases with the number of females per male in the breeding group. Each point is a different genus, some of which are indicated by name. From Clutton-Brock and Harvey (1977).
      • Sexual dimorphism in tooth size
      • Testis size and breeding system
        • Fig. 2.7 Log combined testes weight (g) versus body weight (kg) for different primate genera. Solid circles are multimale breeding systems. Open circles are monogamous. Open triangles are single-male systems (one male with several females). The cross is our own species, Homo, for comparison. From Harcourt et al. (1981). Reprinted with permission from the Nature Publishing Group.
    • Using phylogenies in comparative analysis
      • Species are not independent
      • Phylogenies
        • Fig. 2.8 (a) A simple phylogeny. In this tree, A gave rise to two descendants, B and C, each of which gave rise to two more descendants: D and E, and F and G. The character states (x, y) of the four living species (D, E, F, G) are measured. Those of their ancestors (B and C) have to be estimated. In this case they are assumed to have values intermediate between those of their descendants. There are three independent contrasts in this tree: C1, C2 and C3. (b) Plotting contrasts in x against contrasts in y shows that there has been correlated evolution in these two traits.
      • Independent contrasts
        • Fig. 2.9 Song complexity and brain anatomy in European warblers (family Sylviidae) from the genus Acrocephalus and Locustella. (a) Some species, like the grasshopper warbler L. naevia, have very simple songs (in this species, one syllable is repeated). Others, like the marsh warbler A. palustris, have a complex song with up to a hundred different syllable types in their repertoire. (b) Phylogeny of the Acrocephalus and Locustella warblers. The numbers refer to the eight independent contrasts used in the analysis. (c) Correlation between contrasts in syllable repertoire size and contrasts in volume of the higher vocal centre (HVC) of the brain (corrected for body size). The eight independent contrasts are labelled. From Szekely et al. (1996).
        • Fig. 2.10 Relationship between testis mass and body mass in bushcricket species (Tettigoniidae) with low (filled circles) and high (open circles) degrees of polyandry. Phylogenetic information was incorporated into the statistical analysis by weighting current species values by the distance separating them in the phylogeny. The lines, fitted from a phylogenetic model, are for low (solid line) and high (dashed line) degrees of polyandry. From Vahed et al. (2010).
      • Discrete variables and the order of change during evolution
      • Sexual swellings in female primates
        • Fig. 2.11 Sexual swellings in female chimpanzees (Bossou, Guinea, West Africa). (a) Female on the left with male retreating on the right. Photo © Kathelijne Koops. (b) A 42-year old female carrying her five-year old daughter on her back, being inspected by an adult male. She became pregnant soon after this photo was taken. Photo © Susana Carvalho.
        • Fig. 2.12 Phylogeny of old world monkeys (Purvis, 1995), with some clades collapsed to facilitate presentation of data. The terminal branches are extant species and their traits are indicated. In the left hand column is presence (purple box) or absence (white box) of sexual swellings. In the right hand column is multimale (purple box) or single-male (white box) mating system. The pale shaded boxes indicate taxa with both single-male and multimale mating systems. The ancestral state is most likely that of no swellings. There have been three gains of sexual swellings in this tree (indicated by +1, +2, +3) and two losses (–1, –2). From Nunn (1999). With permission from Elsevier.
        • Fig. 2.13 (a) The correlated evolution of discrete traits. Consider two discrete traits in primates: the first (x) is absence (0) or presence (1) of oestrus advertisement by sexual swellings; the second (y) is a single-male (0) or multimale (1) mating system. The eight arrows indicate the possible transitions between the four states. Statistical methods are used to quantify the evolutionary rates of these transitions in a primate phylogeny and to find the model which best describes the evolutionary transitions. For example, if q1,2 = q3,4, then this implies that the transition to a multimale mating system was independent of the absence or presence of oestrus signals. (b) Flow diagram, showing the statistically most probable evolutionary routes in the primate phylogeny, from an ancestral state of no sexual swellings and a single-male/monogamous mating system (0,0) to a derived state of sexual swellings and a multimale mating system (1,1). Thinnest arrows correspond to transition rates with a high (>94%) posterior probability of being zero. Thickest arrows are the most frequent transitions, with thinner arrows less frequent. The combination of arrows indicates that the mating system changes firstly in evolution (state 0,1) and this then selects for a change in female display to sexual swellings (1,1). The alternative hypothesis, that swellings evolve first (1,0) and this then selects for a multimale system (1,1) is not supported. From Pagel & Meade (2006). With permission of the University of Chicago Press.
        • Fig. 2.14 Sexual swellings in a group of wild chimpanzees studied in an evergreen forest in the Tai National Park, Côte d’Ivorie. (a) Swelling size in 12 females (mean ± SE) aligned to the day of ovulation (day 0). Swellings measured from photographs and ovulation determined by enzyme immunoassays from urine samples. The shaded area indicates the fertile phase, when fertilization is most likely. (b) Alpha male copulation rate (mean ± 1SD) during the phase of maximum swellings. Data from 10 females, aligned to the day of ovulation (day 0). Fertile period shaded. From Deschner et al. (2004). With permission from Elsevier.
    • The comparative approach reviewed
    • Experimental studies of adaptation
      • Fig. 2.15 (a) Black-headed gull removing an eggshell. (b) Results of an experiment in which single hen’s eggs, painted to resemble black-headed gull eggs, were placed in the dunes, near a nesting colony. Those with an empty eggshell next to them (5 cm away) were more likely to be taken by predators (n = 60 in each treatment). From Tinbergen et al. (1963).
      • Optimality models
      • Crows and whelks
        • Fig. 2.16 Dropping of whelks by crows. (a) When whelks are dropped, experimentally, from different heights it is found that fewer drops are needed to break the shell when it is dropped from a greater height. (b) Calculation of the total ascending flight needed to break a shell (number of drops × height of each drop). This is minimized at the height most commonly used by the crows (arrow) From Zach (1979).
    • Summary
    • Further reading
      • Topics for Discussion
  • CHAPTER 3 Economic Decisions and the Individual
    • The economics of carrying a load
      • Starlings
        • Fig. 3.1 Starlings fly from their nest to a feeding site, search for a beak-full of leatherjackets by probing in the grass, then take them home to the nestlings. The question examined in the first part of this chapter is how many items the parent should bring on each trip in order to maximize the rate of delivery of food to the nestlings.
        • Fig. 3.2 (a) The starling’s problem of load size. The horizontal axis shows ‘time’ and the vertical axis shows ‘load’. The curve represents the cumulative number of leatherjackets found as a function of time spent searching. The line AB represents the starling’s maximum rate of delivery of food to the nestlings. This rate is achieved by taking a load of seven leatherjackets on each trip. Two other lines, corresponding to loads bigger (eight) and smaller (one) than seven, are shown to make the point that these loads result in lower rates of delivery (shallower slopes). Note that although the cumulative load is shown here as a smooth curve, in reality it is a stepped line since each food item is a discrete package. (b) When the round trip travel time is increased from short to long the load size that maximizes delivery rate increases from b to b'. (c) When starlings were trained to collect mealworms from a feeder, they brought bigger loads from greater distances. Each dot is the mean of a large number of observations of loads brought from a particular distance. The predicted line goes up in steps because the bird is predicted to change its load size in steps of one worm (of course the mean loads do not have to be integers). The prediction shown here is one based on the model of Fig. 3.2b, but it also includes the refinement of taking into account the energetic costs to the parent of foraging and to the chicks of begging. From Kacelnik (1984).
      • Bees
        • BOX 3.1 THE MARGINAL VALUE THEOREM AND REPRODUCTIVE DECISIONS
          • Fig. B3.1.1 (a) The proportion of eggs fertilized by a male dung fly (Scatophaga stercoraria) as a function of copulation time: results from sperm competition experiments. (b) The predicted optimal copulation time (that which maximizes the proportion of eggs fertilized per minute), given the shape of the fertilization curve and the fact that it takes 156 min to search for and guard a female, is 41 min. The optimal time is found by drawing the line AB. The observed average copulation time, 36 min, is close to the predicted value (Parker, 1970a; Parker & Stuart, 1976) (photo of a pair of dung flies © Leigh Simmons).
        • Fig. 3.3 (a) The relationship between load size (expressed as number of flowers visited) carried home by worker bees and flight time between flowers in a patch. Each dot is the mean of an individual bee and the two lines are predictions based on maximizing efficiency (e) and maximizing rate (r). From Schmid-Hempel et al. (1985). (b) By placing tiny weights on the bee’s back while it is foraging Schmid-Hempel was able to study the bee’s rule of thumb for departure from a patch to go home to the hive with a load of nectar. The weights, in the form of brass nuts, are placed on a fine rod that is permanently glued to the bee’s back. They can be added or removed to simulate loading and unloading. From Schmid-Hempel (1986). With permission from Elsevier.
    • The economics of prey choice
      • Fig. 3.4 Shore crabs (Carcinus maenas) prefer to eat the size of mussel which gives the highest rate of energy return. (a) The curve shows the energy yield per second of handling time used by the crab in breaking open the shell and eating the flesh; (b) the histogram shows the sizes eaten by crabs when offered a choice of equal numbers of each size in an aquarium. From Elner and Hughes (1978).
      • BOX 3.2 A MODEL OF CHOICE BETWEEN BIG AND SMALL PREY (CHARNOV, 1976B; KREBS ET AL., 1977)
      • Fig. 3.5 (a) The apparatus used to test a model of choice between big and small worms in great tits (Parus major). The bird sits in a cage by a long conveyor belt on which the worms pass by. The worms are visible for half a second as they pass a gap in the cover over the top of the belt and the bird makes its choice in this brief period. If it picks up a worm it misses the opportunity to choose ones that go by while it is eating. (b) An example of the results obtained. As the rate of encounter with large worms increases the birds become more selective. The x-axis of the graph is the extra benefit obtained from selective predation. As shown in Box 3.2, the benefit becomes positive at a critical value of S1, the search time for large worms. The bird becomes more selective about the predicted point, but in contrast with the model’s prediction this change is not a step function. From Krebs et al. (1977). With permission from Elsevier.
    • Sampling and information
    • The risk of starvation
      • BOX 3.3 RISK AND OPTIMAL SEQUENCES OF BEHAVIOUR (HOUSTON & MCNAMARA, 1982, 1985)
    • Environmental variability, body reserves and food storing
      • Fig. 3.6 (a) Body reserves and environmental variability. The graph shows the body mass of a captive great tit (one of eight in the experiment) which was transferred from a constant to a variable environment for 12 days before returning to the constant environment. Variability in this experiment was produced by randomly altering the length of the night-time period of no foraging. From Bednekoff & Krebs (1995). (b) Food storing and variability. In this experiment, captive marsh tits (one example is shown) stored more food (left), but did not put on more body reserves (right), in a more variable environment. These results suggest that food storing, like fat storage, is a method of coping with environmental variability: whilst great tits, which do not store food, cope with environmental variability by putting on extra fat reserves, marsh tits store extra food in the environment. The right-hand graph also shows the daily weight trajectory of a marsh tit. In the afternoon, the bird transfers food from its hoards to its body, so reserves rise steeply towards the end of the day From Hurly (1992).
    • Food storing birds: from behavioural ecology to neuroscience
      • Fig. 3.7 This pair of pictures shows an autoradiograph (left) and a photostat (right) of a willow tit tail feather. The upper edge of the dark bands on the autoradiographs indicate that the owner of the feather ate a radioactive labelled seed on that day, the sulfur having been incorporated into a growing feather. Feathers were induced to grow by pulling out the original, and a replacement grows over the next 40 days. The right hand, photostat, images show faint horizontal lines that are daily growth bars. (Brodin & Ekman, 1994). Reprinted with permission from the Nature Publishing Group.
      • Fig. 3.8 (a) A schematic of the experimental design used by Sherry et al. (1981). The birds stored and retrieve food with one eye covered by a little plastic eye cap. In the treatment called ‘same’, the cap was on the same eye for storing and retrieval, but in the ‘switch’ condition the eye cap was changed between storage and retrieval of food. During retrieval, the birds searched for seeds that they had stored 24 hours earlier in moss-filled trays on the floor of an aviary. (b) The percentage of time and of visits made to quadrants of the moss trays with stored seeds during recovery, when searching with the same eye (pale blue) and the other eye (dark blue).
      • Fig. 3.9 (a) Two studies of interspecies comparisons of hippocampal size. Within families of birds, storing species have a larger relative hippocampus. The horizontal axis shows the relative size of the hippocampus for different families of birds, after correcting for the effects of body size and overall forebrain size (i.e. taking into account the fact that larger species will have larger brains). The pale blue points are averages for families that do not store food, whilst the dark blue points are families, or groups of species within families, that do store food. Storers have a larger relative hippocampus. After Krebs (1990). (b) Intraspecies comparisons: the volume of the hippocampus, relative to the rest of the forebrain, of black-capped chickadees (Poecile atricapillus) from Alaska (AK) and Iowa (IA) (left panel), and from Maine (ME), Minnesota (MN) and Washington (WA) (right panel). In the former comparison day length in the winter is shorter in Alaska than in Iowa, although both have very cold winters. In the latter, day length is similar in all three sites, but Washington has a milder winter climate than the other two places. The data show that in harsher winters, either as a result of shorter day length or colder temperatures, the birds have a larger relative hippocampus. After Roth et al. (2011).
    • The evolution of cognition
      • Fig. 3.10 (a) A scrub jay at a food storing tray in an experiment to investigate episodic memory. The coloured blocks provide spatial cues for the bird. Photo © Nicky Clayton. (b) Design of an experiment to test for episodic memory. In treatment (i) the birds are given nuts to store, then 120 h later they are given worms to store. Four hours after that, they are allowed to retrieve items. In treatment (ii), the order of storing is first worms, then nuts. From Clayton & Dickinson (1998). Reprinted with permission from the Nature Publishing Group. See text for explanation.
    • Feeding and danger: a trade-off
      • Fig. 3.11 Hungry sticklebacks normally prefer to attack high density areas of prey but after a model kingfisher was flown over the tank they preferred to attack low density areas. From Milinski and Heller (1978). Reprinted with permission from the Nature Publishing Group.
    • Social learning
      • Fig. 3.12 Two species of sticklebacks. (a) Nine-spined sticklebacks often rely on public information when choosing foraging sites, whereas (b) three-spined sticklebacks rely more on personal sampling of alternative options. Photos © Kevin Laland.
      • Copying and learning facilitation
      • Local traditions
      • Teaching
        • Fig. 3.13 (a) (b) Tandem running in the ant, Temnothorax albipennis. The leader teaches the follower where to go to find food. (Franks and Richardson, 2006). Photos © Tom Richardson.
        • Fig. 3.14 A meerkat pup with a scorpion. Adults teach the pups handling skills for these dangerous prey. (Thornton & McAuliffe, 2006). Photo © Sophie Lanfear.
    • Optimality models and behaviour: an overview
      • Table 3.1 A summary of some of the decisions, currencies and constraints discussed
    • Summary
    • Further reading
      • Topics for Discussion
  • CHAPTER 4 Predators versus Prey: Evolutionary Arms Races
    • Fig. 4.1 Selection for efficient foraging by predators selects for better prey defences, which in turn selects for predator improvements, further prey improvements and so on.
    • Red Queen evolution
      • Table 4.1 Examples of predator adaptations and counter-adaptations by prey.
      • Fig. 4.2 Prey defences include: (a) Camouflage: examples from (i) a moth, (ii) a spider. Photos © Martin Stevens, and (iii) a leaf frog. Photo © Oliver Krüger. (b) Masquerade: (i) this moth caterpillar, Biston betularia, mimics a twig. Photo © Nicola Edmunds. (ii) This first instar alder moth, Acronicta alni, mimics a bird dropping. Photo © Eira Ihalainen. (c) Bright colouration signals toxicity, as in this poison frog, Ranitomeya fantastica. Photo © Kyle Summers. (d) Eyespots: as in this Peacock butterfly. Photo © iStockphoto.com/Willem Dijkstra.
    • Predators versus cryptic prey
      • Testing hypotheses about adaptation
        • Fig. 4.3 Underwing moths, Catocala spp., have cryptic forewings and conspicuously coloured hind wings. This is C. sponsa. Photo © Martin Stevens.
        • Cryptic forewings
          • Fig. 4.4 (a) A blue jay in the testing apparatus. The slides are back projected on a screen in front of the bird. The advance key (see text) is to the left. A mealworm is delivered through the circular red hole if the jay makes a correct response. Photo by Alan Kamil. (b) The jays were more likely to detect Catocala moths on a conspicuous background. A jay pecking indiscriminately at all slides gets a low score on the detection index. From Pietrewicz and Kamil (1981).
        • Polymorphic cryptic colouration
          • BOX 4.1 SEARCH IMAGES
            • Fig. B4.1.1
          • Fig. 4.5 The mean percentage of correct responses by jays when moths are presented in sequences of the same species (runs of either Catocala retecta or Catocala relicta) or in a sequence containing both species in random order. The jays improved their performance when runs of the same species were presented but not when the two species were presented in a mixed sequence. From Pietrewicz and Kamil (1979). Reprinted with permission from AAAS.
          • Fig. 4.6 Apostatic selection occurs when a predator eats more of the commoner prey types than expected from their relative frequency in the environment. This promotes polymorphism in prey, because rarer morphs are more likely to survive.
          • Fig. 4.7 In this experiment, blue jays hunted for digital images of moths on a computer screen (with rewards as in Fig. 4.4). The founding population had equal numbers (80 each) of three morphs, one (dark blue line) being more cryptic. The moth population ‘evolved’ over 50 generations (see text) to a stable distribution of the three morphs, with the more cryptic form becoming the most abundant. From Bond and Kamil (1998). Reprinted with permission from the Nature Publishing Group.
        • Brightly coloured hindwings and eyespots
      • Does even slight concealment confer an advantage?
        • Fig. 4.8 Great tits foraging for artificial cryptic prey. The cost of distinguishing cryptic profitable prey may cause the predator to specialize on other more conspicuous prey. In treatment A, twigs were four times as common as the large prey that resembled them; in B the large prey were four times as common as the twigs. The abundance of conspicuous small prey was constant in A and B. According to an optimal foraging model (similar to those discussed in Chapter 3), it pays the predator to specialize on conspicuous prey in treatment A and on cryptic prey in B. From Erichsen et al. (1980).
    • Enhancing camouflage
      • Disruptive colouration
        • Fig. 4.9 (a) (i) Disruptive patterns on the wing margins of this lime hawk moth conceal the body outline. (ii) An artificial moth with cardboard wings and a mealworm body, pinned to a tree trunk to test the effects of disruptive patterns Photos © Martin Stevens. (b) Results of a field experiment with artificial moths (see text). Disruptive patterns increase survival beyond a cryptic pattern, which in turn survives better than plain black or brown wings. From Cuthill et al. (2005). Reprinted with permission from the Nature Publishing Group.
      • Countershading
        • Fig. 4.10 Countershading. (a) (i) This eyed hawkmoth caterpillar, Smerinthus ocellata, feeds with its ventral surface uppermost. It has a darker ventral surface which, when lit from above combines with the shadow on the dorsal surface (below) to give it a uniform reflectance, which helps to conceal its body shape. (ii) When turned, so it is now illuminated dorsally, the lighter dorsal surface is highlighted and the darker ventral surface is now in shadow, creating a more pronounced gradient and rendering the caterpillar more conspicuous. Photos © Hannah Rowland. (b) An experiment with pastry ‘caterpillars’ pinned to the upper surface of branches in a wood. The countershaded caterpillars (dashed light blue line) survived better than plain dark (red line), plain light (purple line) or reverse-shaded prey (darker ventral surface; dark blue line). From Rowland et al. (2008).
      • Masquerade
    • Warning colouration: aposematism
      • Why bright colours?
        • Fig. 4.11 Brightly coloured prey often have repellent defences. (a) A stinging wasp. Photo © iStockphoto.com/ElementalImaging (b) A red poison dart frog. Photo © Oliver Krüger.
        • Fig. 4.12 Phylogeny of poison frogs (Dendrobatidae) based on molecular genetic analysis. The ant icons indicate two origins of a specialized diet, and a possible third origin is indicated by a question mark. The column of photos on the left shows representative cryptic and non-toxic species. The column on the right shows conspicuous and toxic species (the toxicity of A. zaparo is unknown). Figure from Santos et al. (2003); by courtesy of David Cannatella and Juan Carlos Santos.
        • Fig. 4.13 Cumulative number of conspicuous and cryptic distasteful prey taken in successive trials by chicks. In (a) the green food is cryptic, in (b) the blue food is cryptic. In both experiments, by the end of the trial the distasteful prey has been eaten less when it is conspicuous. From Gittleman and Harvey (1980). Reprinted with permission from the Nature Publishing Group.
      • The evolution of warning colouration
        • Table 4.2 Brightly coloured species of caterpillars of British butterflies are more likely to be aggregated in family groups than cryptic species (Harvey et al., 1983).
    • Mimicry
      • Müllerian mimicry: repellent species look alike
        • Fig. 4.14 Müllerian mimicry. In each case, populations of distantly related species converge on the same brightly coloured warning pattern within a single locality but the patterns vary across their range. (a) North American millipedes of the Apheloria clade (top row) and their mimics in the Brachoria clade (below) in three geographical regions. Photo © Paul Marek. (b) Heliconius erato (top row) and its mimic Heliconius melpomene (bottom row) in three geographical regions of the neotropics. Photo © Bernard D’Abrera and James Mallet. (c) Peruvian Ranitomeya (Dendrobates) frogs from two regions. Ranitomeya imitator (left in both panels) and its mimics R. summersi (left panel) and R. ventrimaculata (right panel). Photo © Jason Brown. From Merrill and Jiggins (2009).
      • Batesian mimicry: cheating by palatable species
        • Fig. 4.15 Batesian mimicry. (a) The highly venemous Sonoran coral snake, Micruroides euryxanthus, is the model for (b) its non-venemous Batesian mimic, the Sonoran mountain kingsnake, Lampropeltis pyromelana. These photographs were taken within 3 km of each other in Arizona. Photos © David W. Pfennig (c) An English pub sign fooled by a Batesian mimic; this is a hoverfly (Syrphidae)! Photo by Francis Gilbert.
    • Trade-offs in prey defences
      • Costs of aposematism
        • Fig. 4.16 Variation in aposematic colouration among individual wood tiger moths, Parasemia plantaginis. (a) The caterpillars vary in the size of the orange patch. (b) The hindwings of female moths vary from bright red to pale orange. Photos © Eira Ihalainen.
      • Conspicuousness versus crypsis
        • Fig. 4.17 Influence of predation on colour pattern of male guppies. (a) Both number of colour spots per fish and spot size are smaller in streams with greater predation. The main predators are other fish and prawns. Data from five streams in Venezuela with increasing levels of predation from A to E. From Endler (1983). (b) A selection experiment in the laboratory. F, foundation population of guppies kept with no predators. S, start of the experiment; predators added to population C but not to population K. Note the rapid change in population C after predation began. I and II are the dates of two censuses. From Endler (1980).
    • Cuckoos versus hosts
      • Fig. 4.18 The common cuckoo, Cuculus canorus, has several genetically different host-races each of which lays a distinctive egg (central column) which matches, to varying extents, the eggs of its particular host species (left-hand column). In the examples here, the host species and their corresponding cuckoo host races are, from top to bottom: robin, pied wagtail, dunnock, reed warbler, meadow pipit and great reed warbler. The right-hand column is of variously coloured model eggs used to test host discrimination. From Brooke and Davies (1988).
      • Fig. 4.19 (a) A female common cuckoo parasitizing a reed warbler nest. Firstly she removes a host egg. Then, holding it in her bill, she sits briefly in the nest and lays her own egg in its place. Photo by Ian Wyllie. (b) A cuckoo egg (right) in a reed warbler nest. (c) A newly-hatched cuckoo chick ejecting host eggs one by one. Photo © Paul Van Gaalen / ardea.com (d) The reed warbler hosts continue to feed the young cuckoo even as it grows to seven times their own weight. Photo © osf.co.uk. All rights reserved.
      • Cuckoos have evolved in response to hosts
        • Fig. 4.20 Seeing eggs through a bird’s eyes (Stoddard & Stevens, 2011). (a) The relative stimulation of the four avian cone types (ultraviolet sensitive, short-, medium- and long-wave sensitive) is determined from reflectance spectra and the spectral sensitivity functions for each cone type. From Hart (2001). With permission from Elsevier (b) Egg colours are mapped in avian tetrahedral colour space; the position of a colour is determined by the relative stimulation of the four retinal cones. (c) Background colours and spot colours are then compared for cuckoo and host eggs. Only background colours are shown here. The overlap between common cuckoo (red) and host (blue) distributions in tetrahedral colour space is shown for various host races of cuckoo. (d) The relationship between host rejection rate of non-mimetic eggs and background colour overlap for eleven cuckoo host races. Colour overlap is expressed as the percentage of the host volume overlapped by the cuckoo volume. Egg photographs by Mary Caswell Stoddard © Natural History Museum, London.
      • Hosts have evolved in response to cuckoos
        • Fig. 4.21 Tawny-flanked prinia eggs (outer circle) and cuckoo finch eggs (inner circle). The diversity of egg ‘signatures’ in the host leads to a signature-forgery arms race between host and cuckoo and remarkable diversity in egg colours and markings within a species. From Spottiswoode and Stevens (2012). Photo by Claire Spottiswoode.
      • The egg arms race: a coevolutionary sequence
      • Egg rejection versus chick rejection as a host defence
        • BOX 4.2 SIGNAL DETECTION (REEVE 1989)
          • Fig. B4.2.1
        • Fig. 4.22 Visual mimicry of host young by Australian bronze-cuckoo (Chalcites) chicks. From left to right: A. Little bronze-cuckoo chick (above) and D. the host’s chick (below), the large-billed gerygone. B. Shining bronze-cuckoo (above) and E. the host’s chick (below), the yellow-rumped thornbill. C. Horsfield’s bronze-cuckoo (above) and F. the host’s chick (below), the superb fairy-wren. From Langmore et al. (2011).
    • Summary
    • Further reading
      • Topics for Discussion
  • CHAPTER 5 Competing for Resources
    • The Hawk–Dove game
      • Table 5.1 The game between Hawk and Dove (Maynard Smith, 1982).
    • Competition by exploitation: the ideal free distribution
      • The ideal free model
        • Fig. 5.1 The ideal free distribution. There is no limit to the number of competitors that can exploit the resource. Every individual is free to choose where to go. The first arrivals will go to the rich habitat. Because of resource depletion, the more competitors the lower the rewards per individual so at point a the poor habitat will be equally attractive. Thereafter, the two habitats should both be filled so that the rewards per individual are the same in each. After Fretwell (1972).
      • Competing for food: sticklebacks and ducks
        • Fig. 5.2 (a) Milinski’s (1979) feeding experiment with six sticklebacks. At time x, end B of the tank had twice the amount of food as end A. At time y the profitabilities were reversed. The pale blue lines indicate the number of fish predicted at end A according to ideal free theory, and the points and dark blue line are the observed numbers (mean of several experiments). (b) Harper’s (1982) feeding experiment with a flock of 33 mallard ducks. In (i) food was thrown into the pond at twice the rate at site A compared to site B. In (ii) the profitabilities were reversed. Pale blue lines indicate the predicted numbers at site A according to ideal free theory. The points and dark blue line are the observed numbers (means of many experiments).
      • Competing for mates: dung flies
        • Fig. 5.3 (a) Male dung flies on a cowpat, waiting to mate with females that come to lay their eggs in the dung. In this photo, there are six searching males. Two pairs are being attacked by another male while the male is guarding his egg-laying female (centre and left), and there is a struggle for possession of a single female (top margin of the pat in the centre). Photo © G. A. Parker. (b) The number of males declines exponentially with time after pat deposition. (c) Given this distribution of stay times, the result is that mating success of males adopting different stay times is about equal, as predicted by the ideal free model. From Parker (1970).
    • Competition by resource defence: the despotic distribution
      • Fig. 5.4 Resource defence. Competitors occupy the rich habitat first of all. At point a this becomes full and newcomers are now forced to occupy the poor habitat. When this is also full (point b), further competitors are excluded from the resource altogether and become ‘floaters’. After Brown (1969).
    • The ideal free distribution with unequal competitors
      • Fig. 5.5 An illustration of how in theory it is difficult to distinguish between a numerical distribution based on the simple ideal free distribution with equal competitors (e) and a distribution with unequal competitors (a–d). The left-hand patch has twice the input rate of that on the right, so the ideal free distribution (e) of 12 equal competitors is 8:4. To illustrate unequal competitors, we imagine that six of the fish (drawn as twice the size) are capable of eating twice as many prey per unit time than the other six. There are now four possible ways of distributing the 12 fish so that the average intake at the two ends is equal (a–d). However, the number of different possible combinations of individuals which achieves each of these distributions varies. Imagine each fish has a name. The 12 fish can be arranged in only one pattern to achieve distribution (a). However, for (b), (c) and (d), there are many ways of arranging the individual fish to achieve the distribution; the numbers of ways are 90, 225 and 20. In short, by chance alone, (c) is the most likely to be observed. Note that it has the same numerical pattern as (e). After Milinski and Parker (1991).
      • Fig. 5.6 (a) The thin lines are a family of fitness curves for habitats of varying quality (leaf size) and competitor density (no. stem mothers per leaf) in the aphid Pemphigus betae. The pale blue horizontal line is the average success for one, two and three stem mothers per leaf. See text for explanation. From Whitham (1980). (b) Stem mother aphids fight for prime positions on a leaf by kicking and pushing. The winner will settle at the base of the mid-rib where food is richest. From Whitham (1979). Reprinted with permission from the Nature Publishing Group.
    • The economics of resource defence
      • Economic defendability
        • Fig. 5.7 (a) The idea of economic defendability. As the amount of resource defended (or territory size) increases, so do the costs of defence. The benefits (e.g. amount of food available) are assumed to increase at first but level off as the resource becomes superabundant in relation to the animal’s capacity to process the resource. Two benefit curves are shown, one for a rich environment and one for a poor environment: the benefit curve rises more steeply in the former because the density of resources is higher. The resource is economically defendable between A and B. Within this range the optimal territory size depends on the currency: for maximizing net gain (B–C) the optimal size is smaller for the rich environment (X) than for the poor one (X') (note that this is where the slopes of the cost and benefit curves are equal). (b) The same model, but with slightly different shaped curves. In this case the optimal territory size to maximize net gain is predicted to increase in a rich environment (X now greater than X'). Therefore, the shapes of the cost and benefit curves are crucial for the predictions that are made! After Schoener (1983).
        • BOX 5.1 THE ECONOMICS OF TERRITORY DEFENCE IN THE GOLDEN-WINGED SUNBIRD (GILL & WOLF, 1975)
      • Shared resource defence
        • Fig. 5.8 (a) A pied wagtail territory owner exploits its riverside territory systematically, feeding along one bank and then back down the other bank (a circuit of about 40 min) to allow time for prey renewal between successive visits to the same stretch. (b) Sharing the territory with a satellite brings benefits in terms of help with defence, but costs in reducing prey renewal times by half when each bird walks half a circuit behind the other. (c) An owner was predicted to share its territory when the rate of renewal of food and the asymptotic abundance of food were above the curve. These combinations represent instances where the owner gains a net benefit in feeding rate because costs of sharing are outweighed by the benefits. The observed outcomes are shown as dots, each one representing a single day: solid dots – satellite accepted, open dots – satellite chased off.From Davies and Houston (1981)
    • Producers and scroungers
      • Fig. 5.9 Two models for how a mixture of producers and scroungers may be maintained in a population. (a) As the proportion of scroungers increases, both producers and scroungers have declining fitness, but producers always do best. Scroungers are poorer quality competitors. (b) There may be no difference in competitive ability. Each behaviour does best when rare. The stable equilibrium frequency of the two is at x, where producers and scroungers have equal fitness. Model (b) after Barnard and Sibly (1981). With permission from Elsevier.
      • Fig. 5.10 Mottley and Giraldeau’s (2000) experiment with spice finches to test the model in Fig. 5.9b. (a) Experimental aviary. On the producer side, birds can sit on little perches (the T shapes) and pull a string to release food into a dish. On the scrounger side, birds have to wait for producers to make food available (see text for details). (b) Results from one flock, showing how foraging rate of producers (p – solid dots) and scroungers (s – open circles) varies with the number of birds in the scrounger compartment. There are six birds in total in the flock. In the graph on the left, the feeding dishes were uncovered and scrounger = producer feeding rate when 2–3 birds of the flock are scroungers. In the right-hand graph, the dishes were covered, which reduced scrounger (but not producer) food access; here equal success occurs when 0–1 birds are scroungers. (c) When all six birds have free access to either side, the numbers converge on the predicted stable equilibrium (shaded areas) over successive days of the experiment. On days 1–8, dishes were covered and on days 9–16 they were uncovered.
    • Alternative mating strategies and tactics
      • Conditional strategies with alternative tactics
        • Natterjack toads: callers and satellites
          • Fig. 5.11 (a) A calling male natterjack toad with a silent satellite male next to him, waiting to intercept any females that are attracted. Photo © Nick Davies. (b) How a male natterjack toad decides whether to be a caller or a satellite. The subject’s call intensity is plotted against the call intensity of his nearest neighbour. Males were predicted to become satellites when their neighbours produced calls twice as loud as their own calls (the area to the left of the dashed line). The open circles refer to males who were satellites and the closed circles males who called. From Arak (1988). With permission from Elsevier.
          • Fig. 5.12 A satellite male horseshoe crab (left) next to a female (front) and guarding male (behind). From Brockmann et al. (1994) and Brockmann (2002).
        • Morphological switches with body size: dung beetles and earwigs
          • Fig. 5.13 (a) Horned (left) and hornless (right) males of the dung beetles: (i) Onthophagus taurus and (ii) O. nigriventris. Photos © Douglas Emlen. (b) Scaling relationship between horn length and body size (thorax width) for 810 taurus males collected from pastures in Durham County, North Carolina. Inserts illustrate the frequency distribution of body sizes and horn length.From Moczek and Emlen (2000). With permission from Elsevier.
          • Fig. 5.14 Alternative mating tactics in Onthophagus dung beetles. Large, horned males guard burrow entrances and fight to defend females. Small, hornless males sneak matings through side tunnels. From Emlen (1997).
          • Fig. 5.15 (a) Gross’s (1996) model for the threshold morphological switch between alternative tactics within a conditional strategy. The fitness of each alternative tactic A and B varies with an individual’s competitive ability. On average tactic B has the lower pay-off. However, below threshold x, B does best while above the threshold A does best. With permission from Elsevier. (b) The reproductive success of horned (solid symbols) and hornless (open symbols) male dung beetles Onthophagus taurus. Horned males begin to do better at a body size of about 5 mm pronotum width, which corresponds to the threshold for horn development in the population under study. Hunt and Simmons (2001).
          • Fig. 5.16 Douglas Emlen’s (1996) artificial selection experiment with Onthophagus dung beetles. Left-hand graph: in one line, he bred from males with larger horns (a) and in the other line from males with smaller horns (b) than expected for their body size. Right-hand graph: after just seven generations the threshold switch to horns differed between the two selection lines.
          • Fig. 5.17 A threshold morphological switch for male forceps length in European earwigs. From Tomkins and Brown (2004). Reprinted with permission from the Nature Publishing Group. (a) The sigmoidal relationship between male forceps length and body size (measured as pronotum width) for two island populations in the North Sea, UK (Bass Rock, open circles; Knoxes Reef, Farne Islands, solid circles). The x axis is the standardized pronotum width for each population (mean zero ±1, 2, 3 standard deviations). The switch to long forceps occurs at a relatively (and absolutely) smaller body size on the Bass Rock, so a greater proportion of the males here has large forceps (proportion with large forceps indicated by length of the yellow bars in the lines below the x axis). (b) Relationship between population density of earwigs and proportion of macrolabic (long forceps) males in the population for 22 islands in the North Sea.
      • Alternative strategies: equilibria and cycles
        • Ruffs: fighters, satellites and female mimics
          • Fig. 5.18 Alternative genetic mating strategies. (a) In the ruff there are three male strategies: territorial males (right) have dark ruffs, satellite males (centre) have white ruffs and female mimics (left) have no ruffs. Photo © Susan McRae. (b) In the marine isopod Paracerceis sculpta there are three male morphs which differ in size and behaviour; from left to right: alpha, beta and gamma males. From Shuster (1989).
        • A marine isopod with three male morphs
        • Side-blotched lizards: cycles of orange, blue and yellow
          • Fig. 5.19 (a) The three male colour morphs of the side-blotched lizard: orange, blue and yellow. Each has a different mating strategy (see text). Photo © Barry Sinervo. (b) Observed frequencies of each male strategy (O, Y, B) in a Californian population from 1990 to 1999. The triangle plots the frequencies as follows: 0–100% blue from base to apex, 0–100% orange from right side to left vertex, and 0–100% yellow from left side to right vertex. Shaded areas indicate the zones where each morph has highest fitness. From Alonzo and Sinervo (2001).
    • ESS thinking
    • Animal personalities
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 6 Living in Groups
    • Fig. 6.1 Living in groups: (a) In winter, tens of thousands of starlings gather in spectacular amoeba-like flocks at dusk, prior to their night-time roost. Photo © osf.co.uk. All rights reserved (b) When a predator approaches, many fish form tight shoals. Why do individuals form groups? How are group movements coordinated? Photo © iStockphoto.com/stevedeneef.
    • Table 6.1 Summary of some anti-predator and foraging benefits of grouping
    • How grouping can reduce predation
      • Diluting the risk of attack
        • Dilution: theory
        • Dilution: evidence
          • Fig. 6.2 An example of the dilution effect. The prey are insects called water skaters (Halobates robustus) that sit on the water surface; their predators are small fish (Sardinops sagax). The fish snap the insects from below, so there is little possibility that vigilance increases with group size. The attack rate by the fish was similar for groups of different sizes, so the attack rate per individual varies only because of dilution. The ‘predicted’ line is what would be expected if the decline in attack rate with group size is entirely caused by dilution; this line is very close to the observed. From Foster and Treherne (1981). Reprinted with permission from the Nature Publishing Group.
          • Table 6.2 Dilution advantage from grouping. Wild horses in the Camargue, southern France, were kept in a group of three or in a group of 36. Although the larger group attracted more biting tabanid flies, individual horses suffered fewer attacks in the larger group (Duncan & Vigne, 1979).
        • Synchrony in time: predator swamping
          • Fig. 6.3 Synchronous emergence swamps predators. The percentage of adult female mayflies Dolania americana preyed upon by aquatic and aerial predators combined, during seven days in June. Individual mayfly are safest on days where more females emerge.From Sweeney and Vannote (1982).
        • Selfish herds
          • Fig. 6.4 (a) W.D. Hamilton’s (1971) model of the selfish herd. Each frog has a ‘domain of danger’ in which it is likely to be selected for attack if a predator appears: this is shown for one individual in (i) as the solid bar, and is the zone stretching half way to the neighbour on either side. Any predator approaching this zone will select this frog as the nearest potential victim. The frog can reduce its zone of danger by jumping to settle in between two closer neighbours (arrowed movement, new domain of danger shown by dashed line). If all frogs follow this principle, the result will be increased aggregation (ii). (b) A test of Hamilton’s model. An experiment with groups of decoy styrofoam seals, attached to a raft using reed poles, and then presented to great white sharks (see text). A shark attacking the decoys. Photo © Claudio Velasquez Rojas/Homebrew Films. (c) An individual seal decoy’s risk of shark attack increased with its domain of danger, as assumed in Hamilton’s model. De Vos and O’Riain (2010).
      • Predator confusion
        • Fig. 6.5 The confusion effect of grouping by prey. The capture success per attack of, from left to right: squid, cuttlefish, pike and perch, when attacking small prey fish in singles, groups of six, or groups of twenty. In all cases, capture success declines with increasing prey group size.From Neill and Cullen (1974).
      • Communal defence
        • Fig. 6.6 Group defence. In dense colonies of guillemots, like this one, breeding success is higher than in sparse colonies because of more effective defence against nest predators such as gulls. From Birkhead (1977). Photo © T. R. Birkhead.
      • Improved vigilance for predators
        • Groups detect predators sooner
          • Fig. 6.7 (a) Goshawks are less successful when they attack larger flocks of wood pigeons. (b) This is largely because bigger flocks take flight at greater distances from the hawk. The experiments involved releasing a trained hawk from a standard distance. From Kenward (1978). (c) Water skaters, Halobates robustus, in larger groups also respond sooner to an approaching model predator, by agitated movements on the water surface when the predator is further away.From Treherne and Foster (1980).
          • Fig. 6.8 Vigilance in groups. (a) An ostrich spends a smaller proportion of its time scanning (head up) when it is in a larger group. (b) The overall vigilance of the group (at least one bird scanning) increases with group size (solid line) and follows the relationship expected if each individual looks up independently of others in the group (broken line).From Bertram (1980). With permission from Elsevier.
        • Response to others’ alarms
        • Cheating
          • Fig. 6.9 The evolutionarily stable vigilance (ESS) for individuals in groups of different sizes (see text for explanation).From McNamara and Houston (1992). With permission from Elsevier.
          • Fig. 6.10 A cheetah (a) is less likely to attack the more vigilant Thomson’s gazelles (b) in a group.Photos © Oliver Krüger.
        • Sentinels
          • Fig. 6.11 Sentinels in: (a) meerkats and (b) pied babblers. These individuals watch for predators from look-out perches while the rest of the group forages. Is the sentinel altruistic or selfish? Photos © Tom Flower.
          • Fig. 6.12 The watchman’s song. Sentinels give quiet vocalizations while on guard. Playback of sentinel calls to foraging pied babblers leads to lower vigilance (a), and improved foraging success (b) by the foragers in the group, compared to control playback of background noise.From Hollen, Bell and Radford (2008). With permission from Elsevier.
    • How grouping can improve foraging
      • Better food finding
      • Better prey capture
        • Fig. 6.13 Group hunting. When they hunt in a group, (a) spotted hyenas and (b) lions can successfully attack prey which are larger than themselves. Photo (a) © Hans Kruuk and (b) © Craig Packer.
        • Fig. 6.14 A pack of fourteen spotted hyenas hunting a group of zebras. The zebra mares and foals run in a tight formation, followed by the stallion, who repeatedly charges at the hyenas.From Kruuk (1972).
        • Fig. 6.15 Cooperative hunting in lions may involve individual specializations. (a) Seven stalking roles taken by lionesses towards a prey: A–B positions are ‘left wings’, C–E are ‘centres’ and F–G are ‘right wings’. (b) Stalking roles of seven lionesses of the Okondeka pride in Etosha National Park, Namibia. The number of hunts is shown above each set of histograms. Individuals clearly differed in their positions: for example, number 34 preferred the ‘left wing’, numbers 4, 27 and 39 were ‘centres’, while numbers 46 and 49 preferred the ‘right wing’.From Stander (1992).
    • Evolution of group living: shoaling in guppies
    • Group size and skew
      • Optimal versus stable group sizes
        • Fig. 6.16 An example of the benefits and costs of group living. (a) (i) A cliff swallow breeding colony. (ii) A bird at its nest entrance. Individuals gain benefit from the colony, which is an information centre enhancing food finding (ephemeral insect swarms; Brown 1988). (b) However, there are also costs; the number of blood-sucking hemipterans (swallow bugs, Oeciacus vicarius) on nestlings increases with colony size and (c) nestling body mass declines with increasing numbers of these ectoparasites. (d) Two nestlings, both 10 days old. The one on the right is from a fumigated nest, where the bugs were removed. The one on the left is from a naturally infested nest in the same colony. Photos (a) and (d) © Charles R. Brown. Figures (b) and (c) from Brown and Brown (1986). With permission of the Ecological Society of America.
        • Fig. 6.17 The idea of optimal group size. (a) As group size increases both benefits and costs increase. However, in theory the increase in benefits will be a decelerating function (with each added individual having less effect than the last), while the increase in costs will accelerate (each added individual having more effect than the last). Therefore, costs will eventually exceed the benefits at large group sizes. (b) In theory, there will be an optimal group size (benefits – costs a maximum) at an intermediate group size. After Krause and Ruxton (2002).
        • Fig. 6.18 Caraco and Wolf’s calculation of optimal hunting group size for lions when hunting wildebeest in the Serengeti. (a) With increasing lion group size, capture success increases (solid circles) but if a kill is made, then food per lion decreases (open triangles). (b) This results in an optimal group size of two lions, to maximize food per lion per chase. Observed group sizes, however, are larger, on average three to four lions per hunt.From Caraco and Wolf (1975).
        • Fig. 6.19 Optimal group sizes may not be stable. In this example individual fitness is maximal at a group size of seven, but a new arrival would do better to join this group than to be solitary because individual fitness in a group of eight is higher than in a group of one. Further individuals should continue to join until the group size is 14. Only after this would the next newcomer do better alone. After Sibly (1983). With permission from Elsevier.
      • Individual differences in a group
        • Skew Theory
        • Queuing by size in groups of coral reef fish
          • Fig. 6.20 Reproductive skew. (a) Size hierarchy in a group of the coral-dwelling goby, Paragobiodon xanthosomus. These individuals were anaesthetised to enable this photo to show the size ratios within the group. Subordinates restrain their growth to avoid being evicted by the dominants. Photo © Marian Wong. (b) A banded mongoose group. Dominant females evict pregnant subordinates when the group size exceeds the optimum from the dominant’s point of view.Photo © Hazel Nichols.
        • Banded mongooses
    • Group decision making
      • Local rules and self-organized groups
        • Traffic lanes in humans and ants
          • Fig. 6.21 (a) (i) A colony of army ants Eciton burchelli on the trail. Photo © Stefanie Berghoff. (ii) Some are taking a large insect prey back to the nest. Photo © Nigel Franks. (b) Ants returning to the nest with food (red curve) tend to occupy the centre of the trail with outbound foragers (blue curve) on the periphery, either side. (c) Individual ants detect the pheromone gradient (shown as a normal distribution about the centre of the trail) with the tips of their two antennae, moving towards the side with the strongest concentration. (d) The result is a straight line movement along the trail or, with some error in detection of pheromone concentration, a sinusoidal trail around the centre. From Couzin and Franks (2003).
        • Local rules in fish shoals
          • Fig. 6.22 (a) Three behavioural zones of an individual fish: A is a zone of repulsion (here individuals move away from others to avoid collision). B is a zone of orientation (here individuals align with the movement of others). C is a zone of attraction (here individuals move towards others). Computer simulations show that different group structures can emerge simply as a result of changes in these zones. (b) With little or no orientation zone, a swarm forms. (c) As the size of the orientation zone increases, the group forms a torus. (d) As the zone of orientation increases still further, the group begins to move in one direction. From Couzin et al. 2002. (e) (f) (g): The three states in golden shinerfish Notemigonus crysoleucas. These are the only states observed in many hours of tracking these fish. Photos courtesy of lain D. Couzin.
          • Fig. 6.23 Shoal size in banded killifish. (a) Median group size in experiments where the treatments were: food odour added to aquarium, control, food odour and alarm odour (extract of broken skin of killifish), and alarm odour only. (b) The variation in observed group sizes across two of the treatments, compared with outcomes of a simulation which varied an individual’s response to neighbours (see text). From Hoare et al. (2004). With permission from Elsevier.
      • Leadership and voting
        • Leaders and followers
        • Voting
          • Table 6.3 Examples of opinion polling and consensus decision making in groups (Conradt & Roper, 2005).
          • Fig. 6.24 Opinion polling in the ant Temnothorax albipennis. (a) Recruitment to potential new nest sites occurs first by tandem running, with the follower signalling its presence by tapping the body of the leader with its antennae. (b) After a sufficient number of workers has voted for a new site, there is more rapid recruitment involving transport; one worker simply carries another one to the site. Photos from Franks et al. (2002). (c) In one study, the switch from tandem runs to transport occurred when there were 20 recruits at a new site.From Pratt (2005).
          • Fig. 6.25 Recruitment to a new nest site by the waggle dance of the honeybee. (a) A scout from a swarm waiting in the left-hand tree has found a potential new nest site in the tree on the right, 1500 m away and 40° clockwise from the sun. (b) The scout performs a waggle dance on the surface of the swarm. She signals the direction of the new nest site by the angle of the waggle run from the vertical, the distance by the duration of the straight waggle run and the quality of the site by the speed with which she repeats the waggle run.From Franks et al. (2002), after Seeley (1995).
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 7 Sexual Selection, Sperm Competition and Sexual Conflict
    • Fig. 7.1 Darwin’s theory of sexual selection was proposed to explain the evolution of traits, usually found in males, concerned with competition for mates, either by force or by charm. (a) Horns of the male kudu Tragelaphus strepsiceros. Photo © Oliver Krüger. (b) Ornaments of the male Raggiana bird of paradise Paradisaea raggiana, left, on display to a female, right. Photo © Tim Laman/naturepl.com
    • Males and females
      • Differences in gamete size
        • Fig. 7.2 Parker et al. (1972) proposed that anisogamy evolved from isogamy by disruptive selection for two gamete sizes: large gametes with food reserves (eggs) and small gametes (sperm) which parasitize the investment of the large gametes.
      • Differences in parental care
    • Parental investment and sexual competition
      • Fig 7.3 A.J. Bateman (1948) put equal numbers of male and female fruit flies (Drosophila melanogaster) in bottles and scored the number of matings and offspring produced by each individual, using genetic markers to assign parentage. For males reproductive success goes up with number of matings, for females it does not, beyond the first mating.
      • Table 7.1 In polygamous or promiscuous species some males have a much higher potential reproductive rate than females
    • Why do females invest more in offspring care than do males?
      • BOX 7.1 MEASURING THE STRENGTH OF SEXUAL SELECTION (KLUG ET AL., 2010)
        • Fig B7.1.1
    • Evidence for sexual selection
      • Traits that improve a male’s success in combat
        • Fig. 7.4 (a) Male southern elephant seal. (b) Two males fighting for harems of females. (c) The male is huge compared to the female. These are two subadults.Photos © Oliver Krüger.
      • Female choice
        • Fig. 7.5 Malte Andersson’s classic experiment showing how male tail length in long-tailed widowbirds influences female choice. Top: Before experimental manipulations, there was no significant difference across the four groups in the mean number of nests per male territory (a measure of the number of females attracted). Bottom: After experimental manipulation, males with elongated tails attracted more females compared to shortened-tail males and controls. The drawing shows the male display flight. After Andersson (1982). Reprinted with permission from the Nature Publishing Group.
        • Fig. 7.6 (a) Male sedge warblers with the largest song repertoires are the first to acquire females in the spring. The size of song repertoire is estimated from sample tape recordings of each male. The results were collected in such a way as to control for the possibilities that older males, or males in better territories, both mate first and have larger repertoires. From Catchpole (1980). (b) The mean ± s.e. response score of five females to repertoires of different sizes. The response score measures sexual behaviour. From Catchpole et al. (1984). Reprinted with permission from the Nature Publishing Group.
    • Why are females choosy?
      • BOX 7.2 MULTIPLE ORNAMENTS IN WIDOWBIRDS AND BISHOPS (EUPLECTES SPP.)
        • Fig. B7.2.1 Red-collared Widowbird. Photo © Warwick Tarboton.
        • Fig. B7.2.2 Red bishop. Photo © Oliver Krüger.
      • Good resources
        • Fig. 7.7 Male bullfrogs compete for good egg-laying territories by wrestling (left). The winners then advertise for females by calling (middle) and females lay their eggs in the male’s territory.From Howard (1978a,b).
        • Fig. 7.8 Female choice for good resources. (a) Female hanging flies (Hylobittacus apicalis) mate with males for longer if the male brings a larger prey item for her to eat during copulation. (b) The male benefits from long copulation because he fertilizes more eggs.From Thornhill (1976).
      • Good genes
        • Fig. 7.9 The bowers of: (a) Satin bowerbird. Photo by Michael & Patricia Fogden/Minden Pictures/FLPA. (b) Spotted bowerbird. Satin bowerbirds prefer blue objects. This bower has feathers and human debris including pens, pieces of plastic and toothbrushes. Spotted bowerbirds prefer green objects, especially Solanum berries.Photo © Joah Madden.
    • Genetic benefits from female choice: two hypotheses
      • Fisher’s hypothesis: females gain attractive sons
      • Good genes for sons and daughters
    • Testing the hypotheses for genetic benefits
      • Fig. 7.10 A male (top) and a group of three female stalk-eyed flies roosting on a root hair. Note the much greater eye span of the male.From Wilkinson and Reillo (1994)
      • BOX 7.3 SEXUAL SELECTION FOR NOSE LENGTH: THE IMPORTANCE OF GENETIC COVARIANCE FOR FISHER’S HYPOTHESIS (LANDE, 1981)
        • Fig. B7.3.1 Genes for long nose and long preference go together in the offspring. The slope of the line represents the degree of association or covariance.
      • Peacocks
        • Fig. 7.11 (a) Male peacock displaying. Photo © Marion Petrie. (b) Males with larger eyespots on their tails sired offspring that survived better. From Petrie (1994).
      • Sticklebacks
        • Fig. 7.12 (a) Male three-spined stickleback in breeding colouration zig-zagging around a gravid female. Photo © Manfred Milinski. (b) Under white light (left graph) females prefer the brighter of two males. The experiment was done with 15 pairs of males and plots their difference in red intensity against the strength of the female preference for the brighter male. The greater the difference in red intensity, the stronger the preference for the brighter male. Under green light (where females are unable to distinguish differences in red) there is no significant preference (right graph). From Milinski and Bakker (1990). Reprinted with permission from the Nature Publishing Group.
    • Sexual selection in females and male choice
      • Female ornaments
        • Fig. 7.13 Sexual ornaments in females. (a) In great crested grebes, both sexes have head-feather ornaments, likely to have evolved through mutual mate choice. Photo © osf.co.uk. All rights reserved. (b) Sexual swellings in a female Chacma baboon, Papio ursinus, from the Cape Peninsula, South Africa.Photo © Esme Beamish.
      • Sex role reversal
        • Fig. 7.14 Sex role reversal. (a) A pair of pipefish Syngnathus typhle. The male is in front, the female is upside down below him. (b) A pregnant male pipefish with a brood pouch full of developing young.Photos © Anders Berglund.
        • Fig. 7.15 The katydid (bush cricket) Kawanaphila nartee from Australia on kangaroo paw flowers. The male produces a large protein-rich spermatophore. (a) A pair together at the end of copulation, with the male (curled up behind the female) depositing his spermatophore. (b) The female bending over to eat the spermatophore. She will use this food to help her form eggs.Photos © Darryl Gwynne.
    • Sex differences in competition
      • Fig. 7.16 Sexual dimorphism in the eclectus parrot. The male is bright green, with red underwing coverts. The female is bright red and blue. Photos © (a) Lochman Transparencies, (b) © Michael Cermak.
    • Sperm competition
      • Table 7.2 Sexual selection operates both before and after mating
      • Why do females copulate with more than one male?
        • Costs of resistance exceed the costs of acquiescence
        • Material (or direct) benefits from multiple mating
        • Genetic (or indirect) benefits
          • Fig. 7.17 A comparative study of bird plumage dimorphism by Owens and Hartley (1998) showed that sexual dimorphism did not correlate with social mating system (number of mates: 0 – social monogamy, 1 to 3 – increasing levels of male polygyny), but increased significantly with extra-bond paternity (percentage offspring sired by extra-bond males). Plumage dimorphism is scored on a scale from zero (no difference between males and females) to ten (males much brighter than females). Circle sizes reflect sample size.
          • Table 7.3 In some song birds, females seek extra-pair matings from males whose display traits are more elaborate than those of their social mates
    • Constraints on mate choice and extra-pair matings
    • Sexual conflict
      • Table 7.4 Sexual conflict: summary of some male and female adaptations and counter-adaptations
      • Sexual conflict over mating
        • Fig. 7.18 (a) A pair of water striders Gerris lacustris engaged in a pre-mating struggle. The female (below) raises up to push the tips of the pair’s abdomens onto the water’s surface tension, which often causes the male to lose his grip. Photo © Ingela Danielsson and Jens Rydell. (b) In some species, like Gerris incognitus, males have evolved grasping genital segments (A) and females have evolved abdominal spines (B), which help the female resist the male’s grip. Other species, like Gerris thoracicus, are less armed and less dimorphic (C male; D female). (c) When indices of armament levels of male and female across different species of Gerris are plotted together, the species tend to fall along a line suggesting sexually antagonistic coevolution, in which increased male armament for grasping is matched by increased anti-grasping defences in females. The most armed species are bottom left (e.g. incognitus) and the least armed are top right (e.g. thoracicus). From Arnqvist and Rowe (2002b). Reprinted with permission from the Nature Publishing Group.
      • Sexual conflict after mating
        • Male adaptations
          • Fig. 7.19 Two sperm displacement mechanisms in Odonata. Crocethemis erythraea: (a) uninflated penis; (b) inflated penis. The horn-like structure repositions sperm of previous males in the spermatheca. Orthetrum cancellatum: (c) the whip-like flagellum is everted during copula; (d) it carries barbs which remove sperm from the narrow ducts of the spermatheca. Siva-Jothy (1984). Photos by Michael Siva-Jothy.
          • Fig. 7.20 In this experiment, female fruit flies Drosophila melanogaster were given varying exposure to male accessory gland proteins (Acps) at mating, while keeping constant other costly aspects of reproduction, such as egg production, non-mating exposure to males and rate of mating. Females exposed to males which produced Acps (dark blue line) died significantly sooner (median lifespan 21 days) than females exposed to three other types of males (median 29 days), namely: males genetically engineered to lack Acps (red line), and two control groups of males (open symbols and pale blue line) which courted females at the normal rate but could not mate because their external genitalia were ablated. From Chapman et al. (1995). Reprinted with permission from the Nature Publishing Group.
          • Fig. 7.21 A pair of feral fowl copulating. The female is fitted with a harness, so sperm can be collected after a mating to measure the ejaculate.Photo © Charlie Cornwallis.
        • Female adaptations
          • Fig. 7.22 (a) Field cricket, Gryllus bimaculatus. Photo © Tom Tregenza. (b) Results of a double mating experiment. Females mated to two of the female’s own siblings suffer reduced hatching success due to inbreeding depression. Females mated to a sibling plus a non-sibling (in either order) do just as well as those mated to two non-siblings, suggesting the female can bias fertilization success in favour of the unrelated male.From Tregenza and Wedell (2002).
    • Sexual conflict: who wins?
      • Fig. 7.23 Coevolution of male and female genitalia in waterfowl. (a) In species where the male has a longer phallus, the female has a more elaborate vagina, with more spirals (right) and ‘dead end pouches’ (left). The vaginal spirals are in the opposite direction to male phallus spirals, suggesting antagonistic rather than mutualistic ‘lock and key’ coevolution. (b) Mallard duck, Anas platyrhynchos, a species with high levels of forced copulations in which the male has a long phallus (bottom right) and the female has a long and elaborate vagina (top left). The white bar is 2 cm.From Brennan et al. (2007).
    • Chase-away sexual selection
      • Fig. 7.24 The phylogeny of the swordtails suggests that the ancestor of the genus Xiphophorus lacked an elongated tail, with the swordtail evolving in the lineage that diverged from the platyfish. Surprisingly, female platyfish and Priapella prefer males of their species with experimentally elongated tails. This suggests that a sensory bias in favour of tails evolved first and that this was then exploited by the swordtail species. (Basolo 1990, 1995). Photo of female and male swordfish Xiphophorus helleri.© Alexandra Basolo.
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 8 Parental Care and Family Conflicts
    • Fig. 8.1 The three types of intra-familial conflict discussed in this chapter. Male and female parents are in conflict over who should invest and how much. Siblings compete over the investment from parents. Offspring have different interests from their parents over supply and demand of investment.From Parker et al. (2002).
    • Evolution of parental care
      • Table 8.1 Sex roles in parental care (Kokko & Jennions, 2008)
      • Birds
      • Mammals
      • Fish
        • Table 8.2 Distribution of male and female parental care with respect to mode of fertilization in teleost fishes. The table shows number of families; a single family may appear in more than one category, but is not listed under ‘no parental care’ unless care is completely unknown in the family (Gross and Shine, 1981)
        • Hypothesis 1: Paternity certainty
        • Hypothesis 2: Order of gamete release
        • Hypothesis 3: Association
    • Parental investment: a parent’s optimum
      • Fig. 8.2 The optimal parental investment per offspring from a parent’s point of view is where the Benefits minus Costs are at a maximum. Increasing investment brings diminishing benefits as the offspring’s needs become saturated, but costs continue to increase because every unit of continued investment deprives other offspring (current and future) of a parent’s limited lifetime resources for care.
    • Varying care in relation to costs and benefits
      • Comparing North and South American passerine birds
        • Fig. 8.3 Responses of North American and South American songbird parents to presentations of: (a) a nest predator (experimental playback of calls of a jay) and (b) a predator of adults (presentation of taxidermic mount of a hawk). Responses measured as reduction in feeding visits to a brood of nestlings. South American parents value their own lives (future broods) more (stronger response to adult predator) while North American parents value their current brood more (stronger response to nest predator). From Ghalambor and Martin (2001). Reprinted with permission from AAAS.
      • Flexible parental response to current brood demands
      • Flexible care in St Peter’s fish
        • Fig. 8.4 St Peter’s fish: a mouth brooder. Photo and drawing © Sigal Balshine. Experiments to test how opportunities for further matings influence: (a) male care and (b) female care in St Peter’s fish. Three conditions are tested: Control (2 male, 2 females); Male bias (3 males, 1 female); female bias (1 male, 3 females). Available females increases male desertion (a), while available males increases female desertion (b).From Balshine-Earn and Earn (1998).
      • Filial cannibalism
      • Varying investment in response to mate attractiveness
    • Sexual conflict
      • Who should care?
        • Table 8.3 An ESS model of parental investment (Maynard Smith, 1977). Each sex has the possibility of caring or deserting. The matrix gives the reproductive success for males and females (see text for details)
      • How much care?
        • Fig. 8.5 Male-female conflict over how much care to provide (Houston & Davies 1985). (a) A male’s best response to the female’s parental effort; (b) a female’s best response to the male’s parental effort. These shallow slopes involve incomplete compensation, so if the partner reduces its effort, the other increases but not sufficiently to compensate for the loss. (c) Plotting both responses together shows that these lead to stable biparental care. Imagine, for example, that the female plays effort x. The male’s best response is one. The female then replies with two, the male with three, the female with four, and so on, reactions proceeding by smaller and smaller amounts until the intersection which is the ESS. (d) If reactions have slopes steeper than one (over-compensation) the intersection is unstable; responses proceed by larger and larger amounts until one parent ends up doing all the work. The reader is invited to start with any female effort and then follow the male’s best response, the female’s best reply, and so on. The ESS is for uniparental care by either male or female. Which parent it is depends on the starting point of the game.
        • Fig. 8.6 Camilla Hinde’s (2006) experiment with great tits. (a) A great tit brood. A speaker is hidden inside the nest, so begging calls of the brood can be augmented by playback. Photo © Simon Evans. (b) Male parent great tit. Photo © Joe Tobias.
        • Table 8.4 Parental response to playback of extra calls (Hinde, 2006) Each parent responded by increasing its provisioning rate to the brood. The partner who did not experience the playback also increased its effort.
    • Sibling rivalry and parent–offspring conflict: theory
      • Fig. 8.7 (a) Intrabrood conflict. A parent with two offspring in a brood; the parent is equally related to both offspring (r = 0.5) but each offspring is more related to itself (r = 1) than to its sibling (r = 0.5, if full sibling). (b) Interbrood conflict. A parent with one offspring per brood. Again it is assumed that the offspring in the next brood is a full-sibling (same father and mother). The current offspring values itself (r = 1) more than its future full sibling (r = 0.5), whereas the parent is equally related to both offspring (r = 0.5).
      • Fig. 8.8 Trivers’s (1974) theory of parent–offspring conflict. The benefits and costs from the parent’s point of view are the same as for Fig. 8.2. However, an offspring will value its own life (r = 1) twice as much as it is valued by its parent (r = 0.5), so the benefit curve for the offspring is twice that for the parent. If siblings are full siblings (r = 0.5) then the cost curve for the offspring is the same as that for the parent (see text). The optimal parental investment from an offspring’s point of view is greater than the parental optimum.From Lazarus and Inglis (1986). With Permission from Elsevier.
    • Sibling rivalry: evidence
      • Facultative siblicide
      • Obligate siblicide
      • Sibling relatedness influences rivalry
        • Fig. 8.9 Sibling conflict within broods of nestling birds increases as relatedness declines. (a) Nestlings beg more loudly in species where there is higher extra-pair parentage (i.e. lower average relatedness between siblings). This significant relationship still holds when controlling statistically for phylogeny, brood size and body mass. The species with 100% extra-pair parentage is the brown-headed cowbird, a brood parasite unrelated to the host young (Briskie et al. 1994). (b) Nestlings also have redder mouths in species with higher extra-pair parentage, but only in species nesting in open nests (solid symbols; solid line), not in those nesting in dark nests (open symbols: dashed line) (Kilner, 1999).
        • Fig. 8.10 (a) American coot chicks have orange-tipped ornamental plumes. Photo © Bruce Lyon. (b) Parental provisioning to broods where all the chicks have had their orange plumes trimmed (black controls) is no different than to normal broods (orange controls). However, in experimental broods where half the chicks have been trimmed, the black chicks are fed less than their orange sibs. (Lyon et al. 1994).
    • Parent–offspring conflict: evidence
      • Behavioural squabbles
        • Table 8.5 Robert Magrath’s (1989) experiment with blackbirds, to test the influence of a brood hierarchy on the parent’s reproductive success. All broods were of four chicks (Synchronous, same size; Asynchronous, different size). Photo of a female blackbird feeding a worm to her chicks © W.B.Carr.
      • Sex ratio conflict
      • Conflicts during pregnancy
      • Conflict resolution
        • Fig. 8.11 Cross-fostering experiments reveal that within families parental supply is coadapted to offspring demand. (a) Great tits: each point refers to a different brood. Offspring begging intensity (measured in a foster-parent’s nest) is correlated with its genetic mother’s generosity (measured as increased provisioning response to begging playbacks). From Kölliker et al. (2000). (b) Burying beetles: each point again refers to a different brood. More generous mothers (response to foster offspring) have offspring which beg more strongly (response measured when raised by a foster mother).From Lock et al. (2004).
        • Fig. 8.12 Cross-fostering experiments with canaries. The growth rate of a foreign brood is greatest when its begging levels match those that the parents expected from their own (focal) brood.From Hinde et al. 2010. Reprinted with permission from AAAS.
    • Brood parasites
      • Fig. 8.13 (a) A brown-headed cowbird chick grows best when it shares the nest with two host young. Each point refers to a different host species. The curve is the fitted polynomial regression. (b) An experiment in which a cowbird chick is raised by eastern phoebe host parents, either on its own (light blue bars) or together with two host young (dark blue bars). The cowbird grows best when it is with host young. From Kilner et al. (2004). Reprinted with permission from AAAS. The photograph shows an eastern phoebe with two of its own chicks (yellow gapes) and a brown-headed cowbird chick.Photo © Marie Read.
      • Fig. 8.14 Vocal and visual trickery by cuckoo chicks. (a) A common cuckoo chick’s vocal trickery in a reed warbler nest. The sonograms, each 2.5 s long, show the begging calls of six day-old chicks recorded in the laboratory one hour after they had been fed to satiation. The cuckoo’s begging calls are much more rapid than a single reed warbler chick and at a week of age are more like those of a whole brood of hungry host chicks. From Davies et al. (1998). (b) A Horsfield’s hawk-cuckoo exposing a false gape – a yellow wing patch – next to its own yellow gape. The host is a blue and white flycatcher Cyanoptila cyanomelana.Photo courtesy of Keita Tanaka.
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 9 Mating Systems
    • Table 9.1 A classification of mating systems
    • Mating systems with no male parental care
      • Fig. 9.1 The two-step process influencing mating systems in cases where males do not provide parental care. Because female reproductive success tends to be limited by resources, whereas male reproductive success tends to be limited by access to females, female dispersion is expected to depend primarily on resource dispersion (modified by predation and benefits and costs of social living), while male dispersion is expected to depend primarily on female dispersion. Males may compete for females directly (A) or indirectly (B), by anticipating how resources influence female dispersion and competing for resource-rich sites.
      • Fig. 9.2 The influence of the spatial distribution of resources (food, nest sites) or mates on the ability of individuals to monopolize more than others. Dots are resources or mates and circles are defended areas. With a patchy distribution of resources or mates there is greater potential for some individuals to ‘grab more than their fair share’.
      • Experimental evidence: voles and wrasse
        • Grey-sided voles, Clethrionomys rufocanus
        • Blue-headed wrasse, Thalassoma bifasciatum
      • Comparative evidence: mammalian mating systems
        • Fig. 9.3 Diversity of mammalian mating systems, illustrated by ungulates. (a) The dik-dik Madoqua kirki is monogamous: a male defends one female, probably because female ranges are too large for a male to defend more than one mate. Courtesy Oxford Scientific Films. Photo by Zig Leszczynski. (b) Male impala Aepyceros melampus defend herds of females temporarily during oestrus. Here a male is preventing a group of three females from leaving his territory. Courtesy Peter Jarman, photo by Martha Jarman. (c) Male Uganda kob Kobus kob thomasi defend tiny territories (15–30 m diameter) on leks and display to attract females. The male in the centre of the photo is mating with a female who has visited his territory. Photo by James Deutsch. (d) In the buffalo Syncerus caffer, several males associate with a large group of females and compete for matings in the multimale group. Courtesy Oxford Scientific Films. Photo by G.I. Barnard.
        • Females solitary: range defensible by male
        • Females solitary: range not defensible by male
        • Females social: range defensible by male
        • Females social: range not defensible by male
      • Leks and choruses
        • Fig. 9.4 On leks, most of the copulations are performed by just a few of the males. (a) Uganda kob Adenota kob thomasi. From Floody and Arnold (1975). (b) White-bearded manakin Manacus manacus trinitatis. From Lill (1974). (c) Sage grouse Centrocercus urophasianus. From Wiley (1973).
        • Males aggregate on ‘hotspots’
        • Males aggregate to reduce predation
          • Fig. 9.5 Male frogs, Physalaemus pustulosus, aggregate into choruses. In larger choruses individuals are safer from predatory bats (a). The number of females attracted also increases with chorus size (b). The curve (2) gives a better fit to the observed points than a straight line (1), which suggests that the number of females per male increases with chorus size. From Ryan et al. (1981). Photo © Alexander T. Baugh.
        • Males aggregate to increase female attraction
        • Males aggregate around attractive ‘hotshot’ males
        • Females prefer male aggregations because these facilitate mate choice
    • Mating systems with male parental care
      • Monogamy
        • Obligate monogamy: fidelity and divorce
          • Fig. 9.6 Effect of pair-bond duration in oystercatchers on: (a) egg survival and (b) annual fledgling production. These ‘adjusted’ measures control statistically for other effects, such as male and female age, individual identity and territory quality. Sample sizes are shown above the x axes. From van de Pol et al. (2006).
          • Fig. 9.7 Two causes of divorce: (a) desertion; (b) usurpation. This cartoon refers to a territorial species, such as the oystercatcher, where the male remains on his territory and the female moves to another territory. The territory where the divorce occurs is shaded. From Ens et al. (1996).
          • Table 9.2 The fitness consequences of divorce for each participant in desertion and usurpation in Fig. 9.7 (Heg et al., 2003)
        • Constrained to be monogamous
          • Fig. 9.8 (a) A male red-winged blackbird displaying his red epaulets. Photo © Bruce Lyon. (b) Reproductive success of male red-winged blackbirds on a marsh in Ontario, Canada, assessed by DNA markers. The fractions in each male territory show the number of chicks sired by the resident male over the total chicks raised. Arrows refer to extra-pair fertilizations (EPF’s): the origin of the arrow shows the identity of the cuckolding male; the arrowhead indicates the territory in which he fertilized chicks; the number in the circle indicates the number of extra-pair chicks he sired. The map shows that most, but not all, cuckolders were near neighbours. From Gibbs et al. (1990). Reprinted with permission from AAAS.
          • BOX 9.1 USING DNA PROFILES TO ASSIGN PARENTAGE
            • Fig. B9.1.1 Using DNA microsatellites to assign paternity in banded mongooses. Photos © Hazel Nichols.
      • Polygyny
        • No cost of polygyny to females
        • Cost of polygyny to females
          • Fig. 9.9 The polygyny threshold model. (a) A female has the choice of settling with an unmated male on a poor quality territory B, or with an already-mated male on a good quality territory A. (b) Female reproductive success increases with territory quality. There is a cost C of sharing with another female, so the curve for the second female in polygyny lies below that for a monogamous female. Provided the difference in territory quality exceeds PT (the polygyny threshold), a female does better by choosing to settle with an already-mated male on territory A rather than with an unmated male on territory B. Modified from Orians (1969).
          • Fig. 9.10 Female settlement patterns predicted by the polygyny threshold model for two distributions (a and b) of male territory quality (territories A to F). It is assumed that the first female does not suffer from the arrival of a second female, so the top line represents the reproductive success of both monogamous (M) females and the first females in polygyny, while the bottom line refers to second females in polygyny. The sequential settlement patterns of six females (1–6) are shown for the six male territories, assuming that females settle where their expected reproductive success is greatest. In both cases two males become polygynous (A and B), two monogamous (C and D) and two remain unmated (E and F). However, settlement patterns and the reproductive success of monogamous versus polygynous females vary depending on the choices available. After Altmann et al. (1977) and Davies (1989).
        • Great reed warblers (Acrocephalus arundinaceus)
        • Red-winged blackbirds (Agelaius phoeniceus)
      • Sexual conflict and polygamy
        • The pied flycatcher (Ficedula hypoleuca)
          • Fig. 9.11 Once a male pied flycatcher has attracted one female, he flies off to another nest site some distance away and tries to attract another. Secondary females suffer because they get little or no help from the male in chick rearing. However, females probably are unable to assess whether the male they pair with has another female because of the large distance between a male’s two nest sites.
        • The dunnock (Prunella modularis)
          • Fig. 9.12 Male dunnock feeding a brood of chicks. Photo © W. B. Carr. (a) Sexual conflict in dunnocks. Female territories (solid lines) are exclusive and may be defended by one or two unrelated males (dashed lines). The numbers refer to the number of young raised per season by males and females in the different mating combinations (maternity and paternity measured by DNA fingerprinting; Burke et al. (1989)). Arrows indicate the directions in which dominant (alpha) male and female behaviour encourage changes in the mating system. A male does best with polygyny; the cost of polygyny to females is shared male care. A female does best with polyandry; the cost of polyandry to males is shared paternity. (b) Polygynandry as a stalemate to the conflict: the alpha male is unable to drive the beta male off to claim polygyny, and neither female can evict the other to claim polyandry. From Davies (1989, 1992).
      • Polyandry threshold
      • Female desertion and sex role reversal
        • Fig. 9.13 Sex role reversal in birds. This male African jacana performs all the parental duties. Females are larger than males and compete for males by defending large territories. Photo © Tony Heald/naturepl.com.
    • A hierarchical approach to mating system diversity
      • Table 9.3 A hierarchical approach to mating system diversity (Owens & Bennett, 1997)
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 10 Sex Allocation
    • BOX 10.1 SEX DETERMINATION
      • Fig. B10.1.1 Temperature dependent sex determination in reptiles. In many reptiles sex is determined by the temperature during development. For example, in (a) the box turtle (Terrapene ornate) and (b) the green turtle (Chelonia mydas), males are produced at cool incubation temperatures and females at warm incubation temperatures. In other species, such as (c) the Australian freshwater crocodile (Crocodylus johnstoni), the opposite pattern occurs, with males produced at relatively high temperatures. Finally, one sex may be preferentially produced at extreme temperatures (both hot and cold), such as (d) the frill-necked dragon (Chlamydosaurus kingii), where both sexes are produced at intermediate temperatures, but only females at extreme temperatures. Photo (a) © Fred Janzen; (b) © Annette Broderick; (c) and (d) © Ruchira Somaweera.
      • Fig. B10.1.2 Example sex ratio responses to incubation temperature in reptiles with temperature-dependent sex determination. Different lines represent different species. From Bull (1980).
    • Fisher’s theory of equal investment
      • Fig. 10.1 Sex ratio evolution in the southern platyfish. When the sex ratio is perturbed away from equal numbers of males and females, it quickly evolves back to this point. The perturbation is towards a female (a) or a male (b) biased sex ratio. Different lines are different replicates. From Basalo (1994). Reprinted with permission from the University of Chicago Press.
    • Sex allocation when relatives interact
      • Local resource competition
        • BOX 10.2 SEX RATIOS WHEN RELATIVES INTERACT
          • Fig. B10.2.1 Selection for biased sex ratios when relatives interact. (a) If sisters compete for resources, then a male-biased sex ratio is favoured to reduce competition between sisters. (b) If sisters cooperate with each other, then a female-biased sex ratio is favoured to facilitate cooperation. Males are blue, females are pink. From West (2009).
        • Fig. 10.2 The sex ratio at birth in primate species where either females, males and females or males are the dispersing sex. The sex ratio is biased towards the dispersing sex. From Silk and Brown (2008). The photo shows chimpanzee by Joan Silk.
        • Fig. 10.3 The distribution of number of queens in a colony for colonies that produce either female (light blue) or male (dark blue) reproductives, in the narrow-headed ant Formica exsecta. Colonies with relatively few queens produced females, whereas colonies with many queens produced males. From Brown and Keller (2000). Photo by Rolf Kümmerli.
      • Local mate competition
        • Fig. 10.4 Sex ratio adjustment in the parasitoid wasp Nasonia vitripennis. A less female-biased sex ratio is produced when larger numbers of females lay eggs in a patch. From Werren (1983). Photo by Michael Clark.
        • Fig. 10.5 The mechanism of sex ratio adjustment in the parasitoid wasp N. vitripennis. Females produced a less female-biased sex ratio in response to the presence of previously parasitized hosts and the presence of other females (photograph shows the red eye mutant used to follow the behaviour of individuals).From Shuker and West (2004). Photo © David Shuker and Stuart West.
      • Local resource enhancement
        • Fig. 10.6 Sex ratio adjustment in the Seychelles warbler. The offspring sex ratios (proportion male) produced on different quality territories in (a) 1993, (b) 1994 and (c) 1995. Mothers produced daughters on high-quality territories and sons on low-quality territories. (d) The data from 1995 are also shown distinguishing between nests that had either one (solid circles) or more than one (open circles) helper already at the nest. When mothers already had more than one helper, they produce sons, irrespective of territory quality. From Komdeur et al. (1997). Reprinted with permission from the Nature Publishing Group. Photo © Martijn Hammers.
        • Fig. 10.7 The correlation between the extent to which sex ratios are adjusted and the benefit provided by the presence of helpers. A more positive extent of sex ratio adjustment signifies a greater tendency to produce offspring of the sex that helps more, in patches where there is a lack of helpers. Across species, the significant positive correlation indicates that sex ratio adjustment is greater in species where the presence of helpers leads to greater fitness benefits. The data points represent (1) laughing kookaburra, (2) sociable weaver, (3) Harris’s hawk, (4) acorn woodpecker, (5) green wood-hoopoe, (6) western bluebird, (7) alpine marmot, (8) redcockaded woodpecker, (9) bell miner, (10) Seychelles warbler and (11) African wild dog. Griffin et al. (2005). Reprinted with permission of the University of Chicago Press. Photo © Andrew Young.
        • BOX 10.3 META-ANALYSIS
    • Sex allocation in variable environments
      • Maternal condition
        • Fig. 10.8 The Trivers and Willard hypothesis. The relative fitness of sons increases more rapidly with maternal quality than that of daughters. Consequently, females in relatively good condition (> t) would do best by producing sons and females in relatively poor condition (< t) would do best by producing daughters. From Trivers and Willard (1973). Reprinted with permission from AAAS.
        • Fig. 10.9 In red deer, the lifetime reproductive success (LRS) of sons (filled circles and solid line) increases more rapidly with their mother’s social rank than daughters (open circles and dashed line). From Clutton-Brock et al. (1984). Photo © Alison Morris.
      • Mate attractiveness
        • Fig. 10.10 Female blue tits which mate males with a brighter UV patch (crown) produced a higher proportion of male offspring. From Griffith et al. (2003). Photo © Joseph Tobias.
      • Environmental sex determination
        • Fig. 10.11 Size and fitness in the shrimp Gammarus duebeni. (a) Larger females laid more eggs. (b) Larger males were more likely to mate. (c) Larger males mated with larger females. (d) When all of the consequences of size are summed, the relative fitness of males increases more rapidly with size than that of females (photograph of a mating pair, where male is the larger individual). From McCabe and Dunn (1997). Photo © Alison Dunn.
      • Sex change
        • Fig. 10.12 Sex changers. Sex change may be from female to male, as in (a) the bluehead wrasse (terminal male); or male to female, as in (b) the Clownfish Amphiprion percula; (c) the common slipper limpet (Crepidula fornicata; photograph of a mating stack, where the largest individuals at the bottom are female and the smaller individuals at the top are male; and (d) the Pandalid shrimp. Photo (a) © Kenneth Clifton; (b) © Peter Buston; (c) © Rachel Collin; (d) © David Shale/naturepl.com
        • BOX 10.4 POPULATION SEX RATIOS, SEX CHANGE AND GONADS
          • Fig. B10.4.1 Sex change from female to male. The relative fitness of males increases more rapidly with age than that of females. Consequently, individuals are selected to mature as females and then change sex to males at age t. Note the similarity to figure 10.8.
          • Fig. B10.4.2 The distribution of population sex ratios in sex changing species that are either (a) female (protogynous) or (b) male (protandrous) first. The population sex ratio tends to be biased towards the first sex. From Allsop and West (2004).
          • Fig. B10.4.3 The correlation between gametic investment and the occurrence of sex change. Species with female first sex change had relatively similar size female gonads, but smaller testes, than species where sex change did not occur. From Molloy et al. (2007).
    • Selfish sex ratio distorters
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 11 Social Behaviours: Altruism to Spite
    • BOX 11.1 CLASSIFYING SOCIAL BEHAVIOURS
      • Table B11.1.1 Classification of social behaviours
    • Kin selection and inclusive fitness
      • Table 11.1 Coefficients of relatedness (r) for descendant and non-descendant kin, calculated as the probability that a gene in one individual is an identical copy, by descent, of a gene in another individual (assuming outbreeding).
      • BOX 11.2 CALCULATION OF r, THE COEFFICIENT OF RELATEDNESS
      • BOX 11.3 MEASURING RELATEDNESS WITH MOLECULAR MARKERS
      • Fig. B11.3 (a) The genetic relatedness (± s.e.) of different members of a meerkat group. From Griffin et al. (2003). (b) The social wasp, P. dominulus. Photo © Alex Wild. (c) Fruting bodies of the slime mould D. discoideum, sprouting from a dead fly and white-tailed deer (Odocoileus virginianus) faeces. Photo © Owen Gilbert.
      • BOX 11.4 INCLUSIVE FITNESS
        • Fig. B11.4.1 Inclusive fitness is the sum of direct and indirect fitness. A key feature of inclusive fitness is that, as defined, it describes the component of reproductive success which an actor can influence, and therefore which they could be appearing to maximize.From West et al. (2007b).
    • Hamilton’s rule
      • Examples of altruism between relatives
        • Cooperation and alarm calls in ground squirrels and prairie dogs
          • Fig. 11.1 Alarm calling by black-tailed prairie dogs to a stuffed badger. For both males (dark blue histograms) and females (light blue), there are significant differences between type A and type B individuals and also between type A and type C. There was, however, no significant difference for either sex between type B and type C. Data are means ±1 SE. From Hoogland (1983). With permission of Elsevier. Photographs show a female making an alarm call, and a stuffed badger that is pulled across ground to simulate the presence of a predator.Both photos © Elaine Miller Bond.
        • Cooperative courtship in wild turkeys
          • Fig. 11.2 A pair of male wild turkeys, Meleagris gallopavo, that have formed a coalition to court females.Photo by Maslowski/National Wild Turkey Federation.
          • Table 11.2 Parameterizing Hamilton’s rule with wild turkeys (Krakauer, 2005). B and C are measured in units of offspring per male.
    • How do individuals recognize kin?
      • Greenbeards
        • Fig. 11.3 Greenbeard genes cause the actor to either provide help to other individuals who have the beard or harm individuals who do not. Photograph of the fire ant, Solenopsis invicta, shows workers executing a queen who does not carry the b allele. From Gardner and West (2010).Photo © Ken Ross.
      • Direct genetic kin discrimination and armpits
        • Fig. 11.4 The life cycle of a slime mould. With permission of Dr. Mary Wu and Dr. Richard Kessin.
      • Environmental cues for kin discrimination
        • Fig. 11.5 Kin recognition in Belding’s ground squirrels. (a) Laboratory experiments: mean number (± 1 SE) of agonistic encounters between pairs of yearling Belding’s ground squirrels in arena tests. Non-siblings reared together (NS.RT) are no more aggressive than siblings reared together (S.RT). However, non-siblings reared apart (NS.RA) are more aggressive than siblings reared apart (S.RA). (b) and (c) Field observations: aggression and cooperation among yearling females which were full or half-sisters (genetic relatedness determined by blood proteins). Full sisters are less aggressive to one another (b), and assist each other more (c). From Holmes and Sherman (1982).Photo of a calling female © George D. Lepp.
        • Fig. 11.6 Kin discrimination and odour in Belding’s grounds squirells. Individuals spent more time investigating cubes which had been rubbed over closer relatives. From Mateo (2002). With permission on the Royal Society. Photograph of a group of pups at the mouth of a burrow.Photo © George D. Lepp.
    • Kin selection doesn’t need kin discrimination
      • Cooperative iron scavenging in bacteria
        • Fig. 11.7 Public goods in bacteria. Bacteria produce a number of factors that they excrete out into the local environment, and which then provide a benefit to the growth or movement of the local population. The factors are open to the problem of cooperation, because ‘free riders’ who did not produce them will still be able to benefit from the production of these factors by others. Iron scavenging siderophore molecules are an example. Other examples include factors which: digest proteins or sugars; break down host tissues; provide structure for growth; kill or repel competitors or predators; aid movement; modulate immune responses; or inactivate antibiotics.
        • Fig. 11.8 Relatedness and cooperation in the bacterium P. aeruginosa. Populations were set up which contained a mixture of cooperative siderophore producers and uncooperative free riders, which did not produce siderophores. When these populations were maintained such that interacting bacteria were highly related, the cooperative siderophore producing cells spread to fixation. In contrast, when they were maintained such that interacting bacteria were less related, the free riders were able to remain in the population.Griffin et al. (2004). Reprinted with permission from the Nature Publishing Group. Photograph shows green siderophore producers and white free riders growing (differentially) on an agar plate where iron is limiting. Photo © Adin Ross-Gillespie.
    • Selfish restraint and kin selection
      • Cannibalism in salamanders
        • Fig. 11.9 Cannibalism in Arizona tiger salamanders. (a) Larvae are more likely to develop as the cannibal morph when reared with non-relatives. (b) Cannibal morphs were more likely to eat individuals to who they were less closely related. From Pfennig and Collins (1993)Reprinted with permission from the Nature Publishing Group. Photograph of a cannibal morph eating a typical morph. Photo © David Pfennig.
    • Spite
      • Fig. 11.10 Spiteful harming of another individual is favoured when this provides a benefit to a secondary recipient to whom the actor is more closely related.
      • Table 11.3 Not spite: example behaviours that have been suggested as spiteful, but are explained much more easily as selfish behaviours that provide a direct benefit to the actor (West & Gardner, 2010).
      • Murderous soldiers in polyembryonic parsitoid wasps
        • BOX 11.5 RELATEDNESS REVISITED
          • Fig. B11.5.1 The geometric view of relatedness. The shaded area shows the proportion of the actors genes shared with three potential recipients (A, B and C) and the population as a whole. As described in the text, the actor is positively related to A, negatively related to B and zero related to C.
        • Fig. 11.11 Attack rates and relatedness in the polyembryonic wasp C. floridanum. Giron et al. (2004). Photograph of a female parasitizing a Trichoplusia ni egg.Photo © Paul Ode.
      • Chemical warfare in bacteria
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 12 Cooperation
    • What is cooperation?
      • Fig. 12.1 Cooperation. (a) Cells of the algae Volvox carteri weismannia form cooperative spherical multicellular groups, which contain up to 8000 small somatic cells arranged at the periphery and a handful of much larger reproductive (germ) cells. This distinction between somatic and reproductive cells is analogous to that between workers and reproductives in the eusocial insects. Photo © Matthew Herron. (b) Banded mongooses (Mungos mungo) live in cooperative mixed sex groups of about 7–50 individuals across a large part of East, Southeast and South-Central Africa. Photo © Andrew Young. (c) An upside-down jellyfish (Cassiopea xamachana) infected with its algal symbiont (Symbiodinium microadriatum). The algae (orange in the photograph) provide the jellyfish with photosynthates in exchange for nitrogen and inorganic nutrients. Photo © Joel Sachs. (d) In social insects, such as this ant species Camponotus hurculeans, some individuals give up the chance to breed independently and instead raise the offspring of others. Photo © David Nash.
    • Free riding and the problem of cooperation
      • Table 12.1 The Prisoner’s dilemma game (Axelrod & Hamilton, 1981); the pay-off to player A is shown with illustrative numerical values
    • Solving the problem of cooperation
      • Fig. 12.2 A classification of the explanations for cooperation. Direct benefits explain mutually beneficial cooperation, whereas indirect benefits explain altruistic cooperation. Note that the mechanisms under direct and indirect can be classified in a number of ways, and that if interactions are between relatives, then mechanisms which lead to direct benefits can also lead to indirect benefits. The special case of greenbeards is not considered in this chapter, because they are likely to be of limited importance and have already been discussed in Chapter 11.From West et al. (2007b). Reprinted with permission of Elsevier.
      • Table 12.2 Four hypotheses for cooperation; kin selection can explain altruistic cooperation, while the other three can explain mutually beneficial cooperation
    • Kin selection
      • Kin discrimination in long-tailed tits
        • Fig. 12.3 Helping and kin discrimination in long-tailed tits. (a) The presence of helpers leads to a roughly linear increase in the rate at which offspring survive until next year and are recruited into the population. From Hatchwell et al. (2004). (b) Individuals that failed to breed, preferentially went and helped at nests of relatives. From Russell and Hatchwell (2001). (c) The churr calls of individuals were similar to those that they had been raised with, rather than those to who they were genetically related. From Sharp et al. (2005). Reprinted with permission from the Nature Publishing Group. Photograph of a helper feeding at a nest. Photo © Andrew Maccoll.
    • Hidden benefits
      • Fig. 12.4 Concealed helper effects in the superb fairy-wren (Malurus cyaneus). (a) The presence of helpers had no influence on the size of chicks reared, but (b) led to the dominant female laying smaller eggs. (c) In a cross-fostering experiment, where groups with same size eggs could be compared, the presence of helpers led to an increase in the size of chicks. (d) The probability of a breeding female surviving to breed in the next year was greater when she had received help.From Russell et al. (2007). Reprinted with permission from AAAS. Photograph of a male. Photo © Geoffrey Dabb.
    • By-product benefit
      • Table 12.3 A cooperative hunting game.; the pay-off to player A is shown with illustrative numerical values
      • Cooperative nest founding in ants
      • Group augmentation in meerkats
        • Fig. 12.5 Group augmentation in meerkats. In larger groups, (a) individuals spent less time on guard, looking out for predators and (b) the annual adult mortality rate was lower. From Clutton-Brock et al. (1999a, b). Reprinted with permission from AAAS. (c) Females help more than males, and the help provided by males drops when they are adults who are about to leave the group. From Clutton-Brock et al. (2002). Reprinted with permission from AAAS. Photo © Andrew Young.
    • Reciprocity
      • Repeated interactions in the Prisoner’s dilemma
      • Reciprocity in animals
        • Humans
          • Fig. 12.6 The amount of money (pounds sterling) paid per litre of milk consumed as a function of week and the image placed next to a notice requesting payment.From Bateson et al. (2006). With permission of the Royal Society. Photograph shows a crime prevention poster produced by the West Midlands Police, UK, following this research. With permission of the West Midlands Police.
        • Non-humans
        • Vampire bats
          • Fig. 12.7 In vampire bats, weight loss after feeding follows a negative exponential decline, with death from starvation occurring at 75 per cent of pre-fed weight at dusk. Therefore a donation of 5 per cent of pre-fed weight when at weight D should cause a donor to lose C hours but will provide B hours to a recipient at weight R.From Wilkinson (1984). Reprinted with permission from the Nature Publishing Group. Photo © Deitmer Nill/naturepl.com
    • Enforcement
      • Infanticide and eviction in meerkats
        • Fig. 12.8 Eviction in meerkats. Evicted females (a) show higher levels of glucocorticoid adrenhal hormone metabolites in their fecal samples, (b) have higher abortion rates and (c) have lower conception rates. From Young et al. (2006). (d) The litters of dominant females (SF) had lower survival rates when one or more of the subordinate females in the group was pregnant when the litter was born. From Young and Clutton-Brock (2006). With permission of the Royal Society. Photograph shows a dominant pinning down a subordinate. Photo © Andrew Young.
      • Punishment in birds and fish
        • Fig. 12.9 Punishment and the cleaner fish Labroides dimidiatus. The figure shows the percentage of prawn items eaten from the Plexiglas plate by individuals during the initial preference test (light blue columns) and after the experimental treatment (dark blue columns). When the removal of prawns led to removal of the plate (to stimulate fleeing) or chasing with the plate (to simulate punishment), the cleaner fish were more likely to feed on the other food type, fish flakes.From Bshary and Grutter (2005). With permission of the Royal Society. The photograph shows an individual feeding on an experimental Plexiglas plate. Photo © Redouan Bshary.
      • Soybeans sanction non-cooperative bacteria
        • Fig. 12.10 Rhizobia which were able to fix nitrogen showed greater growth than rhizobia who were prevented from fixing.From Kiers et al. (2003). Reprinted with permission from the Nature Publishing Group. Photograph shows a split root experiment, where one half of the root system was supplied with air and the other was supplied with a gas mixture where nitrogen had been replaced with argon. Photo © Ford Denison.
    • A case study – the Seychelles Warbler
      • Table 12.4 The direct and indirect benefits of being a helper in the Seychelles warbler, as measured in offspring equivalents (Richardson et al., 2002)
      • Fig. 12.11 Cooperation and kin discrimination in the Seychelles warbler. (a) The provisioning rate of female subordinates (filled circles and solid line) showed a positive relationship with relatedness to the nestlings being fed, whereas the provisioning rate of male subordinates (empty circles and dashed line) did not. (b) The provisioning rate of female subordinates was significantly higher when the dominant female at the nest was the dominant female at the time of their birth, but showed no relationship with the identity of the dominant male.From Richardson et al. (2003). Photo © Martijn Hammers.
    • Manipulation
    • Summary
    • Further reading
      • Topics for Discussion
  • CHAPTER 13 Altruism and Conflict in the Social Insects
    • The social insects
      • The problem
        • Fig. 13.1 Eusocial species exhibit considerable variation within species between the different castes. (a) Castes of the carpenter ant, Camponotus discolor: male (left), queen (right) and worker (bottom). Photo © Alex Wild. (b) The three female castes of the leafcutter ant Acromyrmex echinatior on their fungus garden – a small worker (garden maintenance and brood nursing), large worker (foraging and defence) and winged virgin queen (who will disperse and mate during a nuptial flight, before shedding her wings and founding a new colony. Photo © David Nash. (c) A queen of the termite Macrotermes bellicosus, in her royal chamber, with the king and numerous members of two worker castes (major and minor). Photo © Judith Korb. (d) Pheidologeton affinis marauder ants have one of the most pronounced size differences among workers. This photograph shows a supermajor worker and several minor workers. Photo © Alex Wild. (e) In the social aphid Colophina arma, females develop into either soldiers (left) or reproductives (right). Photo © Harunobu Shibao. (f) In the eusocial Australia gall thrips, Kladothrips morrisi, a female (right) founds the gall, and some of her offspring develop into soldiers (left) that defend the gall from invaders. Photo © Laurence Mound.
        • Fig. 13.2 The existence of different castes in the social insects has allowed evolution to produce an amazing range of morphs that are specialized to particular tasks. Spectacular soldier morphs include: (a) Zootemopsis nevadensis, a dampwood termite whose large jaws are used to fight against competing colonies of the same species; (b) Nasute termite soldiers (Termitidae) can squirt a noxious sticky substance out of their snouts; (c) army ant (Eciton burchelli) soldiers have hooked mandibles to protect against vertebrate predators (humans have been known to use these jaws as ‘stitches’ to seal wounds); note the smaller worker – this species has a relatively complex caste system with at least four types of workers. Other specializations include: (d) soldiers of the turtle ant Cephalotes varians, which use the bizarre disc on their head as a living door to block the nest entrance; (e) the mandibles of the leaf cutter ant Atta texana are used to cut through leaves with a repeated scissoring motion, where the leading mandible is anchored into the leaf and pulls the trailing mandible to make the cut; (f) replete workers of the honeypot ant, Myrmecocystus mexicanus, become engorged with food and hang from the ceilings of chambers deep underground, acting as ‘living storage vessels’. All photos © Alex Wild.
      • The definition of ‘social insect’
      • The importance of social insects
    • The life cycle and natural history of a social insect
      • Fig. 13.3 (a) An incipient colony of Lasius niger with the larvae, pupae and first workers that a founding queen produces after about three months, solely from her own body reserves and a bit of drinking water. Photo © David Nash. (b) As with many insects, dots of paint can be used to distinguish individual ants in colonies being observed. Photo © Francis Ratnieks.
    • The economics of eusociality
    • The pathway to eusociality
    • The haplodiploidy hypothesis
      • Table 13.1 Degrees of relatedness between close relatives in a haplodiploid species (assuming females mate only once).
      • BOX 13.1 CALCULATING COEFFICIENTS OF RELATEDNESS, r, IN HAPLODIPLOID SPECIES
    • The monogamy hypothesis
      • Fig. 13.4 The relatedness of a worker to her sisters and brothers, plotted against the number of times that her mother (the queen) has mated. The relatedness of a worker to her sisters declines from 0.75 to 0.25, whereas the relatedness to a brother is always 0.25 (Boxes 13.1 and 13.2).
      • Fig. 13.5 Monogamy paves the way to eusociality. (a) The haplodiploidy hypothesis relies on individuals being more related to siblings than offspring, making siblings worth more than offspring. As originally envisioned, this appears to have mostly been a red herring. (b) The monogamy hypothesis emphasizes that if an individual is equally related to its siblings and its offspring, even a very slight but consistent efficiency benefit for raising siblings translates into a continuous selective advantage for helping. (c) Without strict monogamy, individuals are more related to their offspring than they are to their siblings, so that a large efficiency benefit is required in order for rearing siblings to be favoured. From West and Gardner (2010).
      • BOX 13.2 COEFFICIENTS OF RELATEDNESS, r, IN HAPLODIPLOID SPECIES WHEN FEMALES MATE MULTIPLY
      • Fig. 13.6 Monogamy and the evolution of eusociality in the Hymenoptera. Shown is a phylogeny of the eusocial Hymenoptera for which female mating frequency data are available. Each independent origin of eusociality is indicated by alternately coloured clades. Clades exhibiting high (i.e. obligate) polyandry (>2 mates) have solid red branches, those exhibiting facultative low polyandry (many mate singly but some mate with two or three males) have dotted red branches and entirely monandrous genera have solid black branches. Mating frequency data are not available for the allodapine bees. From Hughes et al. (2008). Photos from top to bottom: Microstigmus comes by R. Matthews; Lasioglossum malachurum by C. Polidori; Apis mellifera by F.L.W. Ratnieks; Liostenogaster flavolineata by J. Fields; Polistes dominulus and Diacamma sp. by W.O.H. Hughes.
    • The ecological benefits of cooperation
      • The benefits of life insurance
        • Fig. 13.7 Life insurance in the tropical hover wasp, L. flavolineata. The relationship between the number of small brood developing successfully to become large larvae plotted against (a) the post removal group size and (b) the pre-removal group size. Data are shown for control (dark blue) and removal (light blue) nests. From Field et al. (2000). Reprinted with permission from the Nature Publishing Group. Photograph of a female marked with dots of paint. Photo © Maurizio Casiraghi.
      • The benefits of fortress defence
        • Fig. 13.8 Fortress defence in sponge-dwelling shrimps. Plotted are the phylogentically independent comparisons in relative abundance against the independent comparisons in the extent of sociality, using data from 20 species. From Duffy and Macdonald (2010). With permission of the Royal Society. Photograph shows non-breeding workers in the shrimp Synalpheus regalis. Photo © Emmett Duffy.
        • Table 13.2 The two types of social insects, as divided by whether the evolution of eusociality was driven by life insurance or fortress defence (adapted from Queller & Strassmann, 1998).
      • Food distribution
        • Fig. 13.9 (a) Naked mole-rat queen with young and (b) a Damaraland mole-rat. Photo (a) © Neil Bromhall; (b) © Andrew Young.
    • Conflict within insect societies
    • Conflict over the sex ratio in the social hymenoptera
      • Queen–worker conflict
      • Tests of worker–queen conflict
        • Fig. 13.10 Ratio of investment (measured by dry weight) in 21 species of ants. The x-axis is the ratio of female:male weight and the y-axis is the ratio of numbers of males:females in the colony. The lower line is the prediction if the investment ratio is 1:1 and the upper line is 3:1 in favour of females. The data are closer to the 3:1 line, as predicted if workers control the sex ratio. However, some analyses have suggested that things are not so simple, because: (a) dry weight overestimates investment in females, so the average investment is actually closer to 2:1, and (b) queens mate with multiple males in some species, which leads to workers favouring an investment less biased towards females. (To understand how the lines are drawn take the example of a ?:?, weight ratio of 6:1. Equal investment would mean six ?, per ?, and a 3:1 investment ratio in favour of ? would mean a ratio of 2 ?, per ?.) From Trivers and Hare (1976). Reprinted with permission from AAAS. Photograph shows a mating pair of the rover ant, Brachymyrmex patagonicus, in which females are considerably larger than males. Photo © Alex Wild.
      • Split sex ratios
        • Fig. 13.11 Split sex ratios in the wood ant F. truncorum. The distribution of sex allocation (proportional investment in female reproductives) is shown for colonies where the queen had either singly (dark blue) or multiply (light blue) mated. Across data from four years, colonies with singly mated queens tended to produce females and colonies with multiply mated queens tended to produce males. From Sundstrom (1994). Reprinted with permission from the Nature Publishing Group. Photograph of a queen prior to her mating flight. Photo © Lotta Sundström.
      • The mechanisms of sex ratio conflict
        • Fig. 13.12 Hydrocarbons and sex ratios in the wood ant F. truncorum. Across colonies with multiple mated queens, the proportion of females in the reproductive brood was negatively correlated with the variance in the cuticular hydrocarbon profile of the workers. Open circles and solid line are colonies sampled in 1994. Solid circles and dashed line are colonies sampled in 2000. Curves are logistic regression lines. From Boomsma et al. (2003).
        • Fig. 13.13 Queen control in the fire ant Solenopsis invicta. The proportion of male sexuals raised in colonies both before (light blue bars) and five to six weeks after (dark blue bars) queen exchange experiments. In experimental colonies, queens were exchanged between colonies that had been producing primarily male reproductives and colonies that had been producing primarily female reproductives. In control colonies, queens were swapped between colonies producing primarily the same sex. Overall, following the swapping of queens, the colony sex allocation strategy followed that of the queen, not the workers. From Passera et al. (2001). Reprinted with permission from AAAS. Photograph shows a queen looking for a suitable place to start a new colony after her mating flight. Photo © Alex Wild.
    • Worker policing in the social hymenoptera
      • Worker policing in the honeybee
        • Fig. 13.14 Worker policing in the honeybee. The time course of worker- and queen-laid eggs remaining after experimental introduction into a colony. All worker-laid eggs were rapidly removed. Ratnieks and Visscher (1989). Reprinted with permission from the Nature Publishing Group. Photograph shows a worker inspecting and then removing (policing) an egg laid by another worker. Photo © Francis Ratnieks.
        • Fig. 13.15 Variation in level of worker policing across 48 species. Plotted are the phylogentically independent contrasts in the level of worker policing behaviour against the constrasts in relatedness to workers versus queens sons. Higher levels of worker policing are observed in species where workers are less related to the sons of other workers (nephews). From Wenseleers and Ratnieks (2006). With permission of the University of Chicago Press. Photograph shows a worker of the leafcutter ant Acromyrmex echinatior, in which worker policing occurs. Photo © Alex Wild.
      • Worker policing and enforced altruism
        • Fig. 13.16 Policing enforces altruism. Lower levels of worker reproduction are observed in wasp and bee species where worker policing is more effective. From Wenseleers and Ratnieks (2006). With permission of the University of Chicago Press. Photograph shows the common wasp Vespula vulgaris, which has highly effective worker policing (queens mate multiply) and low levels of worker reproduction. Photo © Tom Wenseleers.
    • Superorganisms
    • Comparison of vertebrates with insects
      • Fig. 13.17 Promiscuity and cooperation in birds. (a) The rate of promiscuity was significantly higher in non-cooperative than in cooperative species. (b) In cooperative species, helpers were present at a lower percentage of nests in species with higher rates of promiscuity. Cornwallis et al. (2010). Reprinted with permission from the Nature Publishing Group. Photograph shows the white-fronted bee-eater, a species with low levels of promiscuity (6%) where approximately 50% of nests have helpers. Photo © Erik Svensson.
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 14 Communication and Signals
    • The types of communication
      • Fig. 14.1 The North American funnel-web spider, Agelenopsis aperta. Photo © Visuals Unlimited.
    • The problem of signal reliability
    • Indices
      • Fig. 14.2 Stages of a fight between two red deer stags. The harem holder roars at the challenger (a). Then the pair engage in a parallel walk (b). Finally they interlock antlers and push against each other (c). Photos by Tim Clutton-Brock.
      • BOX 14.1 SEQUENTIAL ASSESSMENT
        • Fig. B14.1.1 Fighting sequence of male cichlid fish, Nannacara anomala. (a) Lateral orientation. (b) Tail beating. (c) Frontal orientation. (d) Biting. (e) Mouth wrestling. (f) The loser (right) gives up. Jakobsson et al. (1979). Drawing by Bibbi Mayrhofer.
        • Fig. B14.1.2 Fighting in the cichlid fish, Nannacara anomala, is more prolonged (a) and escalates to more dangerous stages (b) the more closely the contestants are matched in size. Weight asymmetry is measured as the logarithm of the weight of the heavier fish divided by the weight of the lighter fish (0 = weight ratio of 1, i.e. equal weights). From Enquist and Leimar (1990). With permission from Elsevier.
      • Fighting assessment and deep croaks in toads
        • Fig. 14.3 Medium size males are more likely to attack silenced males when the high-pitched croak of a smaller male was played. However, croaks cannot be the only assessment cue because for either croak pitch there are fewer attacks at large defenders. The strength of a defender’s kick may also be important. From Davies and Halliday (1978). Photo © Jurgen Freund/naturepl.com
      • Red Deer
        • Fig. 14.4 Spectrogram of a red deer roar representing the distribution of the energy (in grey levels) across time (x axis) and frequency (y axis). The first four formants are visible as dark bands of energy (labelled F1 to F4), which decrease throughout the vocalization. The spacing between the formants is shown by the arrowed lines. The overall spacing between the formants (or ‘formant dispersion’) is estimated by linear regression and changes from 339 Hz at the beginning of the roar (corresponding to a 51.7 cm vocal tract) to 243 Hz at the end of the roar (corresponding to a 72 cm vocal tract). Red deer stags have a descended and mobile larynx that enables them to lengthen their vocal tract during roaring, causing the observed drop in formant frequencies. The minimum formant frequencies attained at the end of the roar reflect the fully extended vocal tract and, therefore, communicate information about body size. From Reby and McComb (2003). With permission from Elsevier. Photo © David Reby.
        • Fig. 14.5 Formant frequency, body size and reproductive success in male red deer. The length of the vocal tract can be estimated by the formant frequencies, as longer tracts lead to lower frequencies. The estimated vocal tract length is greater in (a) larger deer and (b) deer with a higher lifetime reproductive success. From Reby and McComb (2003). With permission from Elsevier.
        • Fig. 14.6 As red deer stags roar, they retract their larynx, and hence increase the length of their vocal tract. This results in the production of lower formant frequencies. From Fitch and Reby (2001). With permission of the Royal Society.
        • Fig. 14.7 A male hammerhead bat, Hypsignathus monstrosus. Males compete for mates in leks that contain 30–150 males, by signalling to females with loud honking calls. These calls appear to have a large influence on mating success, with just 6% of the males obtaining 79% of the copulations. Males have a bizarre morphology that was presumably selected because it exaggerates their calls, with an enormous bony larynx that fills their chest cavity and a head with enlarged cheek pouches, inflated nasal cavities and a funnel shaped mouth. Photo © CNRS Photothèque/Devez, Alain R.
    • Handicaps
      • Fig. 14.8 Extravagant signals. (a) The Royal flycatcher, Onychorhynchus coronatus. Photo © Joseph Tobias. (b) Bird of paradise, Paradisaea rubra. Photo © Tim Laman/nature/pl.com (c) The bower of a Vogelkop Gardener Bowerbird, Amblyornis inornata, consists of a cone-shaped hut, in front of which is an area that is kept clear of debris and decorated with items such as flowers, fruit, beetle wings and leaves. Photo © Richard Kirby/naturepl.com. (d) Male superb Lyrebirds, Menura novaehollandiae, have an amazing mimicking ability, producing a song that is a rich mixture of their own song and other sounds that they have heard, such as the songs of other birds, and human noises, ranging from camera shutters to chainsaws to car alarms. Photo © J. Hauke/Blickwinkel/Specialist Stock.
      • Fig. 14.9 The handicap principle and sexual selection. The benefit (B) of producing a costly signal, such as the increased mating success from having an ornament, is assumed to be roughly equal for all males. The cost (C) of producing the costly ornament is assumed to be lower for higher quality males, because they are in better condition and have additional resources to invest in ornament production. In this case, the benefit of producing the ornament only outweighs the cost (B - C > 0) for high quality males, so only high quality males are selected to produce the ornament, making the ornament a reliable signal of male quality. More generally, the handicap principle requires that the cost to benefit ratio is lower for individuals giving stronger signals.
      • Stalk-eyed flies
        • Fig. 14.10 Male eye span and wing size in response to food treatment, in the stalk eyed fly, T. dalmanni. Male eye span (ES) showed a much steeper decline with reduced food than male wing size, female eye span or female wing size. This result held when analysing absolute eye span and wing size (a), as well as when variation in body size was controlled for with multiple regressions (b). From Cotton et al. (2004). With permission of the Royal Society. Photograph of a flying male. Photo © Samuel Cotton.
      • Badges of status
        • Fig. 14.11 Possible badges of status. (a) The black throat patch or bib of male house sparrows (Passer domesticus). Photo © Tony Barakat. (b) The white forehead patch of the collared flycatcher, Ficedula albicollis. Photo © Thor Veen.
        • Fig. 14.12 Portraits of nine P. dominulus foundresses collected in Ithaca, New York, representing some of the diversity in facial patterns. The central wasp has no black clypeus pigmentation, the remaining wasps have one to three spots. In 158 randomly collected foundresses, 19.6% of foundresses had an entirely yellow clypeus, 65.8% had a single black spot, 12.7% had two spots and 1.9% had three spots. On average, 13% of a wasp’s clypeus was pigmented black; this value ranged broadly from 0 to 39%. Photos © Elizabeth Tibbetts.
        • Fig. 14.13 The social cost of a dishonest badge of status in paper wasps. The mounting rate per minute (aggression) of the (a) manipulated (painted) and (b) unmanipulated wasps after dominance was sorted. The different columns correspond to: pairs in which the manipulated wasp was painted to have more (pos), less (neg) or the same (con) number of black spots when the manipulated wasp was the winner or loser of the contest for dominance. The manipulation caused no change in the behaviour of the manipulated wasp (b), but wasps given more spots that lost the contest for dominance experienced higher levels of aggression from the other wasp (a). From Tibbetts and Dale (2004). Reprinted with permission from the Nature Publishing Group. Photograph shows two females battling for dominance. Photo © Elizabeth Tibbetts.
      • The cost (or not) of handicaps and other signals
    • Common interest
      • Fig. 14.14 The honey bee waggle dance provides information about both the distance and direction of nectar sources. After returning to the hive, successful foragers dance in a figure of eight pattern on the vertical comb. Distance to the nectar source is encoded by length of the straight line part of the dance, during which the workers waggle from side to side. The direction of the straight line part of the dance relative to the vertical plane of the honeycomb shows the direction of the nectar source relative to the sun. Photo © Kim Taylor/naturepl.com
      • Quorum sensing in bacteria
        • Fig. 14.15 The hypothesized function of quorum sensing. At low cell densities, a large proportion of the extracellular factors (common goods or exoenzymes) disperse before they can be used, so their production provides little fitness benefit. At high cell densities, a much greater proportion of the extracellular common goods (or the products they produce) can be used. Consequently, the production of extracellular common goods is more efficient and beneficial at higher population densities.
        • Fig. 14.16 Quorum sensing and relatedness in the bacterium Pseudomonas aeruginosa. (a) Quorum sensing signal negative and signal blind cheats invade populations of wild type cooperators over 48 h of growth. The mutants were distinguished from the wild type by labelling with a green fluorescent protein. Light blue and dark blue bars represent the starting and final percentage of cheats in the population, respectively (± s.e.m). (b) The proportion (± s.e.m.) of quorum sensing individuals (wild type) is plotted against time (rounds of growth). Blue points represent relatively low relatedness and red points represent relatively high relatedness. The experiment was started with an equal mixture of the wild type and signal blind mutants that didn’t respond to signal. High relatedness selects for quorum sensing, whereas low relatedness allows mutants that do not respond to signal to be maintained in the population. From Diggle et al. (2007). Reprinted with permission from the Nature Publishing Group. Photograph shows a normal quorum sensing colony (left) and a colony consisting of (signal blind) mutants that do not quorum sense (right). Photo © Steve Diggle.
      • Courtship and receptivity in fruit flies
        • Fig. 14.17 The fruit fly Drosophila subobscura. Photo © Stephen Dalton/naturepl.com.
      • Food calls
    • Human language
    • Dishonest signals
      • Fig. 14.18 Photograph of an anglerfish. Photo © David Shale/naturepl.com.
      • Fork-tailed drongos make deceptive alarm calls
        • BOX 14.2 ALARM CALLS
        • Fig. 14.19 Deceptive alarm calls by drongos. Sonograms from recordings of: (a) drongo-specific alarm calls made in a true (predator present) and false context (no predator present and stealing food); (b) glossy starling alarm calls made by a glossy starling in a true context and mimicked by a drongo in a false context. Meerkats responded for longer (c) and were more likely to abandon food (d) in response to playback of drongo-specific alarm calls than to non-alarm calls, but did not differ in their response to the true or false drongo-specific alarm calls. Meerkats responded for longer (e) and were more likely to abandon food (f) in response to playback of glossy starling alarm calls than to non-alarm calls, but did not differ in their response to the false (drongo-mimicked) and true glossy starling alarm calls. Means ±1 s.e. From Flower (2011). With permission of the Royal Society.
      • Dishonest Weapon Displays in Mantis Shrimp
        • Fig. 14.20 Photograph of a mantis shrimp Gonodactylus bredini. Photo © Jurgen Freund/naturepl.com
    • Summary
    • Further reading
      • TOPICS FOR DISCUSSION
  • CHAPTER 15 Conclusion
    • How plausible are our main premises?
      • Selfish genes or maximizing individuals?
        • BOX 15.1 ADAPTATION AND DESIGN
      • Group selection
        • Fig. 15.1 New group selection. Individuals with the – allele are relatively cooperative, whereas those with the + allele are not. Within groups, individuals with the + allele do relatively better (increase in frequency). Between groups, groups with a higher frequency of the – allele do better and make a greater contribution to the next generation. Whether the – allele spreads depends upon the relative importance of these within and group components. From Harvey (1985).
        • Table 15.1 The fitness of cooperative individuals who perform a cooperative trait (C) and defectors who do not (D). The calculation assumes that the cooperators (C) invest x resources in cooperation, the benefit to cost ratio is three, groups are composed of two individuals, and that benefits are shared amongst all group members. Cooperators would be defined as altruists or ‘weak altruists’ from a group selection perspective, because x > 0, irrespective of the benefit to cost ratio. From the selfish perspective of an individual, C always leads to a higher fitness, irrespective of whether it is in a group with a C (2x > 3x/2) or a D (x/2 > 0). This shows that a behaviour which would be classed as altruistic from a group selection perspective can be selected for because it increases an individual’s direct fitness (West et al. 2007a).
      • The major evolutionary transitions
        • Fig. 15.2 Thomas Hobbes’ Leviathan shows a giant crowned figure, which is composed from over 300 humans. The quote above is from the Book of Job and translates as ‘There is no power on earth to be compared with him’. However, the major transition approach emphasizes that this is exactly what happens on earth, with groups of individuals coming together to form higher level individuals.
        • Table 15.2 The major evolutionary transitions, each of which has led to a new level of complexity (Maynard Smith & Szathmary, 1995)
      • Optimality models and ESSs
        • Fig. 15.3 Coat colour in Soay sheep. Estimated frequency of (a) dark sheep and (b) the TRYP1 G allele (dominant for dark colour) in a population on St Kilda, from 1985 to 2005. From Gratten et al. (2008). Photograph shows individuals with both the dark and light colour morph. Photo © Arpat Ozgul.
    • Causal and functional explanations
      • Fig. 15.4 A diagrammatic section of a prairie dog burrow. A typical burrow has two entrances, one with a low, round ‘dome’ at its entrance and the other with a taller, steeper-sided ‘crater’. The different heights and shapes of the burrow entrances cause air to be sucked out of the crater end and, therefore, in through the dome. From Vogel et al. (1973). Photo © Elaine Miller Bond.
    • A final comment
      • Fig. 15.5 Sex allocation and population recovery in the kakapo (Strigops habroptilus). The kakapo is a highly endangered flightless nocturnal parrot, endemic to New Zealand. Supplementary feeding of females led to the offspring sex ratio changing from 29% to 67% males. This can be explained by the Trivers and Willard (1973) hypothesis, because supplementary feeding would have led to females being in better condition, selecting them to produce sons, as with the red deer of Fig. 10.9. A new supplementary feeding programme was designed to raise the weight of females above the weight threshold (1.5 kg) above which they reproduce, but to keep them below the weight at which they produce an excess of males (2 kg). The figure shows the estimated number of years for the kakapo population to recover to 150 individuals, for different amounts of supplementary feeding, and from either ad libitum feeding (dark blue line) or the redesigned feeding programme (light blue dashed line). From Robertson et al. (2006). With permission of the Royal Society. Photo © Mark Carwardine / naturepl.com
    • Summary
    • Further reading
  • Back Matter
    • References
    • Index

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