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Chapter 51 (Campbell) Chapter 46 (Starr/Taggart) Behavioral Ecology PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Overview: Studying Behavior • Humans have probably studied animal behavior – For as long as we have lived on Earth • As hunters – Knowledge of animal behavior was essential to human survival Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Cranes are birds that have captivated people’s interest – Possibly because they are large and their behavior is easily observed – Males anAd females cranes engage in elaborate courtship rituals involving graceful dance-like movement and synchronized vocalizations Figure 51.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The modern scientific discipline of behavioral ecology – Extends observations of animal behavior by studying how such behavior is controlled and how it develops, evolves, and contributes to survival and reproductive success. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 51.1: Behavioral ecologists distinguish between proximate and ultimate causes of behavior • The scientific questions that can be asked about behavior can be divided into two classes – Those that focus on the immediate stimulus and mechanism for the behavior – Those that explore how the behavior contributes to survival and reproduction Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What Is Behavior? • Behavior – Is what an animal does and how it does it – Includes muscular and nonmuscular activity A male African cichlid with erect fins. Muscular contraction that raise the fins is a behavioral response to a threat to the fish territory. Dorsal fin Anal fin Figure 51.2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Learning – Is also considered a behavioral process Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Proximate Question • Proximate, or “how,” questions about behavior – Focus on the environmental stimuli that trigger a behavior – Focus on the genetic, physiological, and anatomical mechanisms underlying a behavioral act – Example: Red-crowned cranes (Figure 51-1) like many animals breed in the spring. The proximate question could be: How does day length influence breeding of red-crowned cranes? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ultimate Question • Ultimate, or “why,” questions about behavior – Address the evolutionary significance of a behavior – Example: Why did natural selection favor this behavior and not a different one? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ethology • Ethology is the scientific study of animal behavior – Particularly in natural environments Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Mid 20th-century ethologists – Developed a conceptual framework defined by a set of questions • These questions – Highlight the complementary nature of proximate and ultimate perspectives Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fixed Action Patterns • A fixed action pattern (FAP) – Is a sequence of unlearned, innate behaviors that is unchangeable – Once initiated, is usually carried to completion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • A FAP is triggered by an external sensory stimulus – Known as a sign stimulus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In male stickleback fish, the stimulus for attack behavior – Is the red underside of an intruder (a) A male three-spined stickleback fish shows its red underside. Figure 51.3a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • When presented with unrealistic models – As long as some red is present, the attack behavior occurs (b) The realistic model at the top, without a red underside, produces no aggressive response in a male three-spined stickleback fish. The other models, with red undersides, produce strong responses. Figure 51.3b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Proximate and ultimate causes for the FAP attack behavior in male stickleback fish BEHAVIOR: A male stickleback fish attacks other male sticklebacks that invade its nesting territory. PROXIMATE CAUSE: The red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback. Figure 51.4 ULTIMATE CAUSE: By chasing away other male sticklebacks, a male decreases the chance that eggs laid in his nesting territory will be fertilized by another male. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Imprinting • Imprinting is a type of behavior – That includes both learning and innate components and is generally irreversible Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Imprinting is distinguished from other types of learning by a sensitive period – A limited phase in an animal’s development that is the only time when certain behaviors can be learned Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • An example of imprinting is young geese – Following their mother Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Konrad Lorenz showed that – When baby geese spent the first few hours of their life with him, they imprinted on him as their parent Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • There are proximate and ultimate causes for this type of behavior BEHAVIOR: Young geese follow and imprint on their mother. PROXIMATE CAUSE: During an early, critical developmental stage, the young geese observe their mother moving away from them and calling. ULTIMATE CAUSE: On average, geese that follow and imprint on their mother receive more care and learn necessary skills, and thus have a greater chance of surviving than those that do not follow their mother. Figure 51.5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Conservation biologists have taken advantage of imprinting – In programs to save the whooping crane from extinction Figure 51.6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 51.2: Many behaviors have a strong genetic component • Biologists study the ways both genes and the environment – Influence the development of behavioral phenotypes • Behavior that is developmentally fixed – Is called innate behavior and is under strong genetic influence Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Directed Movements • Many animal movements – Are under substantial genetic influence • These types of movements – Are called directed movements Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kinesis • A kinesis – Is a simple change in activity or turning rate in response to a stimulus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Sow bugs – Become more active in dry areas and less active in humid areas Moist site under leaf Dry open area (a) Kinesis increases the chance that a sow bug will encounter and stay in a moist environment. Figure 51.7a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Taxis • A taxis – Is a more or less automatic, oriented movement toward or away from a stimulus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Many stream fish exhibit positive rheotaxis (rheos – Greek for current) – Where they automatically swim in an upstream direction Direction of river current (b) Positive rheotaxis keeps trout facing into the current, the direction from which most food comes. Figure 51.7b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Migration • Many features of migratory behavior in birds – Have been found to be genetically programmed Figure 51.8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal Signals and Communication • In behavioral ecology – A signal is a behavior that causes a change in another animal’s behavior • Communication – Is the reception of and response to signals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Animals communicate using – Visual, auditory, chemical, tactile, and electrical signals • The type of signal used to transmit information – Is closely related to an animal’s lifestyle and environment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemical Communication • Many animals that communicate through odors – Emit chemical substances called pheromones Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • When a minnow or catfish is injured – An alarm substance in the fish’s skin disperses in the water, inducing a fright response among fish in the area (a) Minnows are widely dispersed in an aquarium before an alarm substance is introduced. Figure 51.9a, b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) Within seconds of the alarm substance being introduced, minnows aggregate near the bottom of the aquarium and reduce their movement. Auditory Communication • Experiments with various insects – Have shown that courtship songs are under genetic control EXPERIMENT Charles Henry, Lucía Martínez, and ent Holsinger crossed males and females of Chrysoperla plorabunda and Chrysoperla johnsoni, two morphologically identical species of lacewings that sing different courtship songs. SONOGRAMS Chrysoperla plorabunda parent Standard repeating unit Volley period Vibration volleys crossed with Chrysoperla johnsoni parent Volley period Standard repeating unit The researchers recorded and compared the songs of the male and female parents with those of the hybrid offspring that had been raised in isolation from other lacewings. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RESULTS The F1 hybrid offspring sing a song in which the length of the standard repeating unit is similar to that sung by the Chrysoperla plorabunda parent, but the volley period, that is, the interval between vibration volleys, is more similar to that of the Chrysoperla johnsoni parent. F1 hybrids, typical phenotype Volley period Standard repeating unit CONCLUSION The results of this experiment indicate that the songs sung by Chrysoperla plorabunda and Chrysoperla johnsoni are under genetic control. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Genetic Influences on Mating and Parental Behavior • A variety of mammalian behaviors – Are under relatively strong genetic control Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Research has revealed the genetic and neural basis – For the mating and parental behavior of male prairie voles Prairie voles are monogamous and help with the nurturing of young, which is very uncommon in mammals Figure 51.11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 51.3: Environment, interacting with an animal’s genetic makeup, influences the development of behaviors • Research has revealed – That environmental conditions modify many of the same behaviors Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Dietary Influence on Mate Choice Behavior • One example of environmental influence on behavior – Is the role of diet in mate selection by Drosophila mojavensis (Fruit Fly) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Laboratory experiments have demonstrated – That the type of food eaten during larval development influences later mate choice in females EXPERIMENT William Etges raised a D. mojavensis population from Baja California and a D. mojavensis population from Sonora on three different culture media: artificial medium, agria cactus (the Baja host plant), and organ pipe cactus (the Sonoran host plant). From each culture medium, Etges collected 15 male and female Baja D. mojavensis pairs and 15 Sonoran pairs and observed the numbers of matings between males and females from the two populations. RESULTS When D. mojavensis had been raised on artificial medium, females from the Sonoran population showed a strong preference for Sonoran males (a). When D. mojavensis had been raised on cactus medium, the Sonoran females mated with Baja and Sonoran males in approximately equal frequency (b). 100 With Baja males (a) With Sonoran males Proportion of matings by Sonoran females 75 (b) 50 25 0 Artificial Organ pipe cactus Agria cactus Culture medium CONCLUSION Figure 51.12 The difference in mate selection shown by females that developed on different diets indicates that mate choice by females of Sonoran populations of D. mojavensis is strongly influenced by the dietary environment in which larvae develop. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Therese Markow and Eric Toolson proposed – That the physiological basis for the observed mate preferences was differences in hydrocarbons in the exoskeletons of the flies Figure 51.13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Social Environment and Aggressive Behavior • Cross-fostering studies in California mice and white-footed mice – Have uncovered an influence of social environment on the aggressive and parental behaviors of these mice Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Influence of cross-fostering on male mice Table 51.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Learning • Learning is the modification of behavior – Based on specific experiences • Learned behaviors – Range from very simple to very complex Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Habituation • Habituation – Is a loss of responsiveness to stimuli that convey little or no information Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spatial Learning • Spatial learning is the modification of behavior – Based on experience with the spatial structure of the environment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In a classic experiment, Niko Tinbergen – Showed how digger wasps use landmarks to find the entrances to their nests EXPERIMENT A female digger wasp excavates and cares for four or five separate underground nests, flying to each nest daily with food for the single larva in the nest. To test his hypothesis that the wasp uses visual landmarks to locate the nests, Niko Tinbergen marked one nest with a ring of pinecones. Nest After the mother visited the nest and flew away, Tinbergen moved the pinecones a few feet to one side of the nest. RESULTS When the wasp returned, she flew to the center of the pinecone circle instead of to the nearby nest. Repeating the experiment with many wasps, Tinbergen obtained the same results. Nest CONCLUSION Figure 51.14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings No Nest The experiment supported the hypothesis that digger wasps use landmarks to keep track of their nests. Cognitive Maps • A cognitive map – Is an internal representation of the spatial relationships between objects in an animal’s surroundings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Associative Learning • In associative learning – Animals associate one feature of their environment (such as color) with another Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Classical conditioning is a type of associative learning – In which an arbitrary stimulus is associated with a reward or punishment Before stimulus Influx of alarm substances Influx of water alone Influx of pike odor Day 1 Relative activity level Day 3 Example: Pavlov dog experiment Figure 51.15 Control group Experimental group Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control group Experimental group • Operant conditioning is another type of associative learning (also called trial and error learning) – In which an animal learns to associate one of its behaviors with a reward or punishment and then tends to repeat or avoid that behavior Having received a face full of quills a young coyote has probably learned to avoid porcupines Figure 51.16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cognition and Problem Solving • Cognition is the ability of an animal’s nervous system to perceive, store, process, and use information gathered by sensory receptors Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Problem solving can be learned – By observing the behavior of other animals Chimpanzees learning to crack oil palm nuts by observing an experienced chimpanzees Figure 51.17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Genetic and Environmental Interaction in Learning • Genetics and environment can interact – To influence the learning process of complex behavior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 51.4: Behavioral traits can evolve by natural selection • Because of the influence of genes on behavior – Natural selection can result in the evolution of behavioral traits in populations Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavioral Variation in Natural Populations • When behavioral variation within a species – Corresponds to variation in the environment, it may be evidence of past evolution Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Variation in Prey Selection • Differences in prey selection in populations of garter snakes – Are due to prey availability and are evidence of behavioral evolution – Foraging: behavior associated with recognizing, searching for, capturing, and consuming food. Garter snake will eat different based on where the snake is living (coastal versus inland) (a) A garter snake (Thamnophis elegans) Figure 51.18a, b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) A banana slug (Ariolimus californicus); not to scale Variation in Aggressive Behavior • Funnel spiders living in different habitats – Exhibit differing degrees of aggressiveness in defense and foraging behavior Desert grassland population 60 50 Time to attack (seconds) Aggressiveness of funnel web spiders from different environments. The arid environments delay less before attacking because of having less food Riparian population 40 30 20 10 0 Field Lab-raised generation 1 Population Figure 51.19 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lab-raised generation 2 Experimental Evidence for Behavioral Evolution • Laboratory and field experiments – Can demonstrate the evolution of behavior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Laboratory Studies of Drosophila Foraging Behavior • Studies of Drosophila populations raised in highand low-density conditions – Show a clear divergence in behavior linked to specific genes 14 Low population density Average path length (cm) 12 High population density 10 8 6 4 2 0 L1 L2 L3 H1 H2 D. Melanogaster lineages Figure 51.20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings H3 H4 H5 Migratory Patterns in Blackcaps • Field and laboratory studies of Blackcap birds – Have documented a change in their migratory behavior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Birds placed in funnel cages – Left marks indicating the direction they were trying to migrate (a) Blackcaps placed in a funnel cage left marks indicating the direction in which they were trying to migrate. Figure 51.21a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Migratory orientation of wintering adult birds captured in Britain – Was very similar to that of laboratory-raised birds N BRITAIN W E S (b) Wintering blackcaps captured in Britain and their laboratory-raised offspring had a migratory orientation toward the west, while young birds from Germany were oriented toward the southwest. N Young from SW Germany Mediterranean Sea Figure 51.21b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings E W S Adults from Britain and F1 offspring of British adults • Concept 51.5: Natural selection favors behaviors that increase survival and reproductive success • The genetic components of behavior – Evolve through natural selection • Behavior can affect fitness – Through its influence on foraging and mate choice Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Foraging Behavior • Optimal foraging theory – Views foraging behavior as a compromise between the benefits of nutrition and the costs of obtaining food • Such as the energy expenditure or risk of being eaten by a predator while foraging. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy Costs and Benefits • Reto Zach – Conducted a cost-benefit analysis of feeding behavior in crows • The crows eat molluscs called whelks – But must drop them from the air to crack the shells Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Zach determined that the optimal flight height in foraging behavior – Correlated with a fewer number of drops, indicating a trade-off between energy gained (food) and energy expended 50 Average number of drops 100 40 Average number of drops 30 75 Total flight height 20 Drop height preferred by crows 10 0 Figure 51.22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 3 5 Height of drop (m) 50 25 7 15 Total flight height (number of drops drop height) 125 60 • In bluegill sunfish – Prey selection behavior is related to prey density Small prey at middle distance In feeding on water fleas the fish do not feed randomly but select prey based on both size and distance, tending to pursue prey that looks largest. Small prey at close distance Large prey at far distance Low prey density Small prey Medium prey Large prey High prey density 14% 33% 33% 33% 35% 50% Percentage available Small prey Medium prey Large prey 33% 33% 33% 100% Predicted percentage in diet Small prey Medium prey Large prey 32.5% 32.5% 35% Figure 51.23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2% 40% 57% Observed percentage in diet Risk of Predation • Research on mule deer populations – Has shown that predation risk affects where the deer choose to feed Predation risk Relative deer use 70 60 20 15 50 40 10 30 20 5 10 0 0 Open Figure 51.24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Forest edge Habitat Forest interior Relative deer use Predation occurrence (%) Optimal foraging theory predicts that prey will forage in a way that minimizes the risks of predation. The risk of predation by mountain lions is lowest in open areas and forest interiors and highest in forest edges Mating Behavior and Mate Choice • Mating behavior – Mating behavior, which includes seeking or attracting mates, choosing among potential mates and competing for mates. – Is the product of a form of natural selection called sexual selection Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mating Systems and Mate Choice • The mating relationship between males and females – Varies a great deal from species to species Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In many species, mating is promiscuous – With no strong pair-bonds or lasting relationships Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In monogamous relationships – One male mates with one female (a) Since monogamous species, such as these trumpeter swans, are often monomorphic, males and females are difficult to distinguish using external characteristics only. Figure 51.25a Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In a system called polygyny – One male mates with many females – The males are often more showy and larger than the females Figure 51.25b (b) Among polygynous species, such as elk, the male (left) is often highly ornamented. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In polyandrous systems – One female mates with many males – The females are often more showy than the males Figure 51.25c (c) In polyandrous species, such as these Wilson’s phalaropes, females (top) are generally more ornamented than males. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The needs of the young – Are an important factor constraining the evolution of mating systems • The certainty of paternity – Influences parental care and mating behavior Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In species that produce large numbers of offspring – Parental care is at least as likely to be carried out by males as females Parental care by a male jawfish. Male jawfish live in tropical marine environments, hold they have fertilized in their mouths, keeping them aerated and protecting them from egg predators Eggs Figure 51.26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sexual Selection and Mate Choice • In intersexual selection – Members of one sex choose mates on the basis of particular characteristics • Example: courtship songs • Intrasexual selection – Involves competition among members of one sex for mates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Mate Choice by Females • Male zebra finches – Are more ornate than females, a trait that may affect mate choice by the females Figure 51.27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Imprinting of female chicks on males with more ornamentation Experimental Groups Both parents ornamented Males ornamented Control Group Females ornamented Parents not ornamented – Affects mate selection as adults Results Females reared by ornamented parents or ornamented fathers preferred ornamented males as mates. Females reared by ornamented mothers or nonornamented parents showed no preference for either ornamented or nonornamented males. Males reared by all experimental groups showed no preference for either ornamented or nonornamented female mates. Figure 51.28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The size of eyestalks in stalk-eyed flies – Affects which males the females choose to mate with Figure 51.29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Male Competition for Mates • Agonistic behavior – Is a source of intrasexual selection that can reduce variation among males Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Such competition may involve agonistic behavior (an often ritualized contest that determines which competitor gains access to a resource) – An often ritualized contest that determines which competitor gains access to a resource Figure 51.30 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Morphology affects the mating behavior – In isopods of the same species that are genetically distinct Large Paracerceis males defend harems of females within intertidal sponges. Tiny males are able to invade and live within large harems. Figure 51.31 males mimic female morphology and behavior and do not elicit a defensive reponse in males and so are able to gain access to guarded harems. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Applying Game Theory • Game theory evaluates alternative behavioral strategies in situations – Where the outcome depends on each individual’s strategy and the strategy of other individuals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Mating success of male side-blotched lizards – Was found to be influenced by male polymorphism and the abundance of different males in a given area 1st (Orange throat lizard) most aggressive and defend territory (More females) 2nd (Blue throat lizard) also territorial but defend a smaller territories (Fewer females) 3rd (Yellow throat lizard) Nonterritorial males that mimic females and use “sneaky” tactics to obtain Figure 51.32 mating Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Concept 51.6: The concept of inclusive fitness can account for most altruistic social behavior • Many social behaviors are selfish • Natural selection favors behavior – That maximizes an individual’s survival and reproduction Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Altruism • On occasion, some animals – Behave in ways that reduce their individual fitness but increase the fitness of others • This kind of behavior – Is called altruism, or selflessness Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • In naked mole rat populations – Nonreproductive individuals may sacrifice their lives protecting the reproductive individuals from predators The naked mole rat (nearly hairless and blind) lives in colonies of 75 to 250 + individuals. Each colony only has one queen who mates with one to three kings. The rest are nonreproductive males and females that forage for underground roots and tubers. The nonreproductive rats sacrifice their own lives to protect their queens and kings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 51.33 Inclusive Fitness • Altruistic behavior can be explained by inclusive fitness – The total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables close relatives to produce offspring Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hamilton’s Rule and Kin Selection • Hamilton proposed a quantitative measure – For predicting when natural selection would favor altruistic acts among related individuals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The three key variables in an altruistic act are – The benefit to the recipient – The cost to the altruist – The coefficient of relatedness Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • The coefficient of relatedness – Is the probability that two relatives may share the same genes Parent A Parent B OR 1/ 1/ (0.5) probability Figure 51.34 Sibling 1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (0.5) probability 2 Sibling 2 2 • Natural selection favors altruism when the benefit to the recipient – Multiplied by the coefficient of relatedness exceeds the cost to the altruist • This inequality – Is called Hamilton’s rule Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Kin selection is the natural selection – That favors this kind of altruistic behavior by enhancing reproductive success of relatives Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • An example of kin selection and altruism – Is the warning behavior observed in Belding’s ground squirrels Mean distance moved from natal burrow (m) 300 Male 200 100 Female 0 0 2 Figure 51.35 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 3 4 12 13 14 Age (months) 15 25 26 Reciprocal Altruism • Altruistic behavior toward unrelated individuals – Can be adaptive if the aided individual returns the favor in the future • This type of altruism – Is called reciprocal altruism Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Social Learning • Social learning – Forms the roots of culture • Culture can be defined as a system of information transfer through observation or teaching – That influences the behavior of individuals in a population Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mate Choice Copying • Mate choice copying – Is a behavior in which individuals in a population copy the mate choice of others Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • This type of behavior – Has been extensively studied in the guppy Poecilia reticulata Control Sample Male guppies with varying degrees of coloration Female guppies prefer males with more orange coloration. Experimental Sample Female model engaged in courtship with less orange male Figure 51.36 Female guppies prefer less orange males that are associated with another female. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Social Learning of Alarm Calls • Vervet monkeys – Produce a complex set of alarm calls when they see a leopard, eagles or snake Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Infant monkeys give undiscriminating alarm calls at first – But learn to fine-tune them by the time they are adults Figure 51.37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • No other species – Comes close to matching the social learning and cultural transmission that occurs among humans Figure 51.38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolution and Human Culture • Human culture – Is related to evolutionary theory in the distinct discipline of sociobiology Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Human behavior, like that of other species – Is the result of interactions between genes and environment • However, our social and cultural institutions – May provide the only feature in which there is no continuum between humans and other animals Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings