1 Chapter 51 Animal Behavior

2 An animal’s behavior is its response to external and internal stimuli Behavior helps an animal Obtain food Find a partner for sexual reproduction Maintain homeostasis Behavior is subject to natural selection

3 Ethology is the scientific study of animal behavior, particularly in natural environmentsAccording to early ethologist Niko Tinbergen, four questions should be asked about behavior: What stimulus elicits the behavior, and what physiological mechanisms mediate the response? How does the animal’s experience during growth and development influence the response mechanisms?

4 How does the behavior aid survival and reproduction?What is the behavior’s evolutionary history? These questions highlight the complementary nature of proximate and ultimate perspectives

5 Proximate causation, or “how” explanations, focus onEnvironmental stimuli that trigger a behavior Genetic, physiological, and anatomical mechanisms underlying a behavior Ultimate causation, or “why” explanations, focus on Evolutionary significance of a behavior

6 Behavioral ecology is the study of the ecological and evolutionary basis for animal behaviorIt integrates proximate and ultimate explanations for animal behavior

7 Fixed Action Patterns A fixed action pattern is a sequence of unlearned, innate behaviors that is unchangeable Once initiated, it is usually carried to completion A fixed action pattern is triggered by an external cue known as a sign stimulus

8 In male stickleback fish, the stimulus for attack behavior is the red underside of an intruderWhen presented with unrealistic models, as long as some red is present, the attack behavior occurs

9 Fig. 51-3 (a) Figure 51.3 Sign stimuli in a classic fixed action pattern (b)

10 Oriented Movement Environmental cues can trigger movement in a particular direction Kinesis and Taxis A kinesis is a simple change in activity or turning rate in response to a stimulus For example, sow bugs become more active in dry areas and less active in humid areas Though sow bug behavior varies with humidity, sow bugs do not move toward or away from specific moisture levels

11 Moist site under leaf Dry open area Sow bug Fig. 51-4Figure 51.4 A kinesis

12 A taxis is a more or less automatic, oriented movement toward or away from a stimulusMany stream fish exhibit a positive taxis and automatically swim in an upstream direction This taxis prevents them from being swept away and keeps them facing the direction from which food will come

13 Migration is a regular, long-distance change in location Animals can orient themselves using The position of the sun and their circadian clock, an internal 24-hour clock that is an integral part of their nervous system The position of the North Star The Earth’s magnetic field

14 Fig. 51-5 Figure 51.5 Migration

15 Some behaviors are linked to lunar cyclesBehavioral Rhythms Some animal behavior is affected by the animal’s circadian rhythm, a daily cycle of rest and activity Behaviors such as migration and reproduction are linked to changing seasons, or a circannual rhythm Some behaviors are linked to lunar cycles For example, courtship in fiddler crabs occurs during the new and full moon

16 Animal Signals and CommunicationIn behavioral ecology, a signal is a behavior that causes a change in another animal’s behavior Communication is the transmission and reception of signals Animals communicate using visual, chemical, tactile, and auditory signals The type of signal is closely related to lifestyle and environment

17 Honeybees show complex communication with symbolic languageA bee returning from the field performs a dance to communicate information about the position of a food source

18 (a) Worker bees (b) Round dance (food near) (c) Waggle danceFig. 51-8 (a) Worker bees (b) Round dance (food near) (c) Waggle dance (food distant) A 30° Figure 51.8 Honeybee dance language C B Beehive 30° Location A Location B Location C

19 Pheromones Many animals that communicate through odors emit chemical substances called pheromones Pheromones are effective at very low concentrations 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

20 Concept 51.2: Learning establishes specific links between experience and behaviorInnate behavior is developmentally fixed and under strong genetic influence Learning is the modification of behavior based on specific experiences

21 Habituation Habituation is a simple form of learning that involves loss of responsiveness to stimuli that convey little or no information For example, birds will stop responding to alarm calls from their species if these are not followed by an actual attack

22 Imprinting Imprinting is a behavior that includes learning and innate components and is generally irreversible It is distinguished from other learning by a sensitive period A sensitive period is a limited developmental phase that is the only time when certain behaviors can be learned

23 An example of imprinting is young geese following their motherKonrad Lorenz showed that when baby geese spent the first few hours of their life with him, they imprinted on him as their parent Conservation biologists have taken advantage of imprinting in programs to save the whooping crane from extinction Young whooping cranes can imprint on humans in “crane suits” who then lead crane migrations using ultralight aircraft

24 Fig (a) Konrad Lorenz and geese Figure Imprinting (b) Pilot and cranes

25 Video: Bee PollinatingSpatial Learning Spatial learning is a more complex modification of behavior based on experience with the spatial structure of the environment Niko Tinbergen showed how digger wasps use landmarks to find nest entrances Video: Bee Pollinating

26 EXPERIMENT Nest Pinecone RESULTS Nest No nest Fig. 51-11Figure Does a digger wasp use landmarks to find her nest? Nest No nest

27 Cognitive Maps A cognitive map is an internal representation of spatial relationships between objects in an animal’s surroundings For example, Clark’s nutcrackers can find food hidden in caches located halfway between particular landmarks

28 Associative Learning In associative learning, animals associate one feature of their environment with another For example, a white-footed mouse will avoid eating caterpillars with specific colors after a bad experience with a distasteful monarch butterfly caterpillar

29 Classical conditioning is a type of associative learning in which an arbitrary stimulus is associated with a reward or punishment For example, a dog that repeatedly hears a bell before being fed will salivate in anticipation at the bell’s sound

30 It is also called trial-and-error learningOperant conditioning is a type of associative learning in which an animal learns to associate one of its behaviors with a reward or punishment It is also called trial-and-error learning For example, a rat that is fed after pushing a lever will learn to push the lever in order to receive food For example, a predator may learn to avoid a specific type of prey associated with a painful experience

31 Fig Figure Operant conditioning

32 Cognition and Problem SolvingCognition is a process of knowing that may include awareness, reasoning, recollection, and judgment For example, honeybees can distinguish “same” from “different”

33 Video: Chimp Cracking NutProblem solving is the process of devising a strategy to overcome an obstacle For example, chimpanzees can stack boxes in order to reach suspended food Some animals learn to solve problems by observing other individuals For example, young chimpanzees learn to crack palm nuts with stones by copying older chimpanzees Video: Chimp Cracking Nut

34 Fig Figure A young chimpanzee learning to crack oil palm nuts by observing an experienced elder

35 Development of Learned BehaviorsDevelopment of some behaviors occurs in distinct stages For example a white-crowned sparrow memorizes the song of its species during an early sensitive period The bird then learns to sing the song during a second learning phase

36 Concept 51.3: Both genetic makeup and environment contribute to the development of behaviorsAnimal behavior is governed by complex interactions between genetic and environmental factors

37 Experience and BehaviorCross-fostering studies help behavioral ecologists to identify the contribution of environment to an animal’s behavior A cross-fostering study places the young from one species in the care of adults from another species In humans, twin studies allow researchers to compare the relative influences of genetics and environment on behavior

38 Table 51-1 Table 51.1

39 Regulatory Genes and BehaviorA master regulatory gene can control many behaviors For example, a single gene controls many behaviors of the male fruit fly courtship ritual Multiple independent genes can contribute to a single behavior For example, in green lacewings, the courtship song is unique to each species; multiple independent genes govern different components of the courtship song

40 EXPERIMENT SOUND RECORDINGS Chrysoperla plorabunda parent:Fig EXPERIMENT SOUND RECORDINGS Chrysoperla plorabunda parent: Volley period Standard repeating unit Vibration volleys crossed with Chrysoperla johnsoni parent: Volley period Standard repeating unit Figure Are the songs of green lacewing species under the control of multiple genes? RESULTS F1 hybrids, typical phenotype: Volley period Standard repeating unit

41 Genetically Based Behavioral Variation in Natural PopulationsWhen behavioral variation within a species corresponds to environmental variation, it may be evidence of past evolution Case Study: Variation in Migratory Patterns Most blackcaps (birds) that breed in Germany winter in Africa, but some winter in Britain The two migratory populations are genetically distinct

42 Fig. 51-15 EXPERIMENT RESULTSScratch marks RESULTS Figure Are differences in migratory orientation within a species genetically determined? N Adults from Britain and offspring of British adults BRITAIN W E S GERMANY N Young from SW Germany W E S

43 Case Study: Variation in Prey SelectionThe natural diet of western garter snakes varies by population Coastal populations feed mostly on banana slugs, while inland populations rarely eat banana slugs Studies have shown that the differences in diet are genetic The two populations differ in their ability to detect and respond to specific odor molecules produced by the banana slugs

44 Fig Figure Western garter snake from a coastal habitat eating a banana slug

45 Influence of Single-Locus VariationDifferences at a single locus can sometimes have a large effect on behavior For example, male prairie voles pair-bond with their mates, while male meadow voles do not The level of a specific receptor for a neurotransmitter determines which behavioral pattern develops

46 Fig Figure A pair of prairie voles (Microtus ochrogaster) huddling

47 Concept 51.4: Selection for individual survival and reproductive success can explain most behaviorsGenetic components of behavior evolve through natural selection Behavior can affect fitness by influencing foraging and mate choice

48 Foraging Behavior Natural selection refines behaviors that enhance the efficiency of feeding Foraging, or food-obtaining behavior, includes recognizing, searching for, capturing, and eating food items

49 Evolution of Foraging BehaviorIn Drosophila melanogaster, variation in a gene dictates foraging behavior in the larvae Larvae with one allele travel farther while foraging than larvae with the other allele Larvae in high-density populations benefit from foraging farther for food, while larvae in low-density populations benefit from short-distance foraging Natural selection favors different foraging behavior depending on the density of the population

50 Low population density 6 High population densityFig 7 Low population density 6 High population density 5 Mean path length (cm) 4 3 2 Figure Evolution of foraging behavior by laboratory populations of Drosophila melanogaster 1 R1 R2 R3 K1 K2 K3 D. melanogaster lineages

51 Optimal Foraging ModelOptimal foraging model views foraging behavior as a compromise between benefits of nutrition and costs of obtaining food The costs of obtaining food include energy expenditure and the risk of being eaten while foraging Natural selection should favor foraging behavior that minimizes the costs and maximizes the benefits

52 Optimal foraging behavior is demonstrated by the Northwestern crowA crow will drop a whelk (a mollusc) from a height to break its shell and feed on the soft parts The crow faces a trade-off between the height from which it drops the whelk and the number of times it must drop the whelk

53 Researchers determined experimentally that the total flight height (which reflects total energy expenditure) was minimized at a drop height of 5 m The average flight height for crows is 5.2 m

54 Average number of dropsFig 125 60 50 100 40 Average number of drops Average number of drops 30 75 Total flight height (number of drops  drop height in m) Total flight height 20 Drop height preferred by crows = 5.23 m 50 Figure Energy costs and benefits in foraging behavior 10 25 2 3 5 7 15 Drop height (m)

55 Balancing Risk and RewardRisk of predation affects foraging behavior For example, mule deer are more likely to feed in open forested areas where they are less likely to be killed by mountain lions

56 Mating Behavior and Mate ChoiceMating behavior includes seeking or attracting mates, choosing among potential mates, and competing for mates Mating behavior results from a type of natural selection called sexual selection

57 Mating Systems and Parental CareThe mating relationship between males and females varies greatly from species to species In many species, mating is promiscuous, with no strong pair-bonds or lasting relationships In monogamous relationships, one male mates with one female Males and females with monogamous mating systems have similar external morphologies

58 (a) Monogamous speciesFig (a) Monogamous species (b) Polygynous species Figure Relationship between mating system and male and female forms (c) Polyandrous species

59 (a) Monogamous speciesFig a Figure 51.20a Relationship between mating system and male and female forms (a) Monogamous species

60 In polygamous relationships, an individual of one sex mates with several individuals of the other sex Species with polygamous mating systems are usually sexually dimorphic: males and females have different external morphologies Polygamous relationships can be either polygynous or polyandrous

61 Consider bird species where chicks need a continuous supply of foodNeeds of the young are an important factor constraining evolution of mating systems Consider bird species where chicks need a continuous supply of food A male maximizes his reproductive success by staying with his mate, and caring for his chicks (monogamy)

62 Certainty of paternity influences parental care and mating behaviorConsider bird species where chicks are soon able to feed and care for themselves A male maximizes his reproductive success by seeking additional mates (polygyny) Females can be certain that eggs laid or young born contain her genes; however, paternal certainty depends on mating behavior Certainty of paternity influences parental care and mating behavior

63 Paternal certainty is relatively low in species with internal fertilization because mating and birth are separated over time Certainty of paternity is much higher when egg laying and mating occur together, as in external fertilization In species with external fertilization, parental care is at least as likely to be by males as by females

64 Fig Eggs Figure Paternal care by a male jawfish

65 Sexual Selection and Mate ChoiceIn intersexual selection, members of one sex choose mates on the basis of certain traits Intrasexual selection involves competition between members of the same sex for mates

66 Mate Choice by Females Female choice is a type of intersexual competition Females can drive sexual selection by choosing males with specific behaviors or features of anatomy For example, female stalk-eyed flies choose males with relatively long eyestalks Ornaments, such as long eyestalks, often correlate with health and vitality

67 Male Competition for MatesMale competition for mates is a source of intrasexual selection that can reduce variation among males Such competition may involve agonistic behavior, an often ritualized contest that determines which competitor gains access to a resource

68 Fig Figure Agonistic interaction

69 Applying Game Theory In some species, sexual selection has driven the evolution of alternative mating behavior and morphology in males The fitness of a particular phenotype (behavior or morphology) depends on the phenotypes of other individuals in the population Game theory evaluates alternative strategies where the outcome depends on each individual’s strategy and the strategy of other individuals

70 For example, each side-blotched lizard has a blue, orange, or yellow throat, and each color is associated with a specific strategy for obtaining mates There is a genetic basis to throat color and mating strategy

71 Like rock-paper-scissors, each strategy will outcompete one strategy, but be outcompeted by the other strategy The success of each strategy depends on the frequency of all of the strategies; this drives frequency-dependent selection

72 Concept 51.5: Inclusive fitness can account for the evolution of altruistic social behaviorNatural selection favors behavior that maximizes an individual’s survival and reproduction These behaviors are often selfish

73 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 For example, under threat from a predator, an individual Belding’s ground squirrel will make an alarm call to warn others, even though calling increases the chances that the caller is killed

74 Inclusive Fitness Altruism can be explained by inclusive fitness Inclusive fitness is the total effect an individual has on proliferating its genes by producing offspring and helping close relatives produce offspring

75 Hamilton’s Rule and Kin SelectionWilliam Hamilton proposed a quantitative measure for predicting when natural selection would favor altruistic acts among related individuals Three key variables in an altruistic act: Benefit to the recipient (B) Cost to the altruist (C) Coefficient of relatedness (the fraction of genes that, on average, are shared; r)

76 Parent A Parent B  1/2 (0.5) probability 1/2 (0.5) probabilityFig Parent A Parent B  OR Figure The coefficient of relatedness between siblings 1/2 (0.5) probability 1/2 (0.5) probability Sibling 1 Sibling 2

77 Natural selection favors altruism when:rB > C This inequality is called Hamilton’s rule Kin selection is the natural selection that favors this kind of altruistic behavior by enhancing reproductive success of relatives

78 An example of kin selection and altruism is the warning behavior in Belding’s ground squirrelsIn a group, most of the females are closely related to each other Most alarm calls are given by females who are likely aiding close relatives Nonreproductive individuals increase their inclusive fitness by helping the reproductive queen and kings (their close relatives) to pass their genes to the next generation

79 Mean distance (m) moved from birthplaceFig 300 Male 200 Mean distance (m) moved from birthplace 100 Figure Kin selection and altruism in Belding’s ground squirrels Female 1 2 3 4 12 13 14 15 25 26 Age (months)

80 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 Reciprocal altruism is limited to species with stable social groups where individuals meet repeatedly, and cheaters (who don’t reciprocate) are punished Reciprocal altruism has been used to explain altruism between unrelated individuals in humans

81 Social Learning Social learning is learning through the observation of others and forms the roots of culture Culture is a system of information transfer through observation or teaching that influences behavior of individuals in a population Culture can alter behavior and influence the fitness of individuals

82 Case Study: Mate-Choice CopyingIn mate-choice copying, individuals in a population copy the mate choice of others This type of behavior has been extensively studied in the guppy Poecilia reticulata Females who mate with males that are attractive to other females are more likely to have sons that are attractive to other females

83 Female guppies prefer males that are associated with another female.Fig Control Sample Male guppies with varying degrees of coloration Female guppies prefer males with more orange coloration. Experimental Sample Figure Mate choice copying by female guppies (Poecilia reticulata) Female model in mock courtship with less orange male Female guppies prefer males that are associated with another female.

84 Learning and problem solvingFig. 51-UN1 Imprinting Learning and problem solving Spatial learning Cognition Associative learning Social learning