Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 55 LECTURE SLIDES

Behavioral Biology Chapter 54

Behavior is what an animal does Proximate causation –Mechanisms that are the reason for behavior –Increased level of testosterone –Neural connections Ultimate or evolutionary causation –Why did this behavior evolve? –Determine how behavior influences reproductive success or survival 3

Behavior 4 levels of analysis 1.Physiology –How it is influenced by hormones, nerve cells, and other internal factors 2.Ontogeny –How it develops in an individual 3.Phylogeny –Its origin in groups of related species 4.Adaptive significance –Its role in survival and fitness 4

Ethology Study of the natural history of behavior Innate behavior –Instinctive, does not require learning –Preset paths in nervous system –Genetic – fixed action pattern –Goose replacing an egg from her nest 5

Innate behavior Egg retrieval behavior is triggered by a key or sign stimulus –Egg out of nest Innate releasing mechanism –Perception of key stimulus and triggering of motor program (fixed action pattern) –Once pattern begins, it goes to completion; even if the egg is removed 6

Nerve Cells, Neurotransmitters, Hormones, and Behavior Behavioral biologists examine the relationship of hormones to behavior to understand the endocrine mechanisms that are the foundation of reproduction, parental care, aggression, and stress Neuroscientists may measure levels of neurotransmitters such as serotonin and dopamine in the nervous system or blood and associate these chemicals with behavior Techniques of neuroethology include identifying and mapping individual neurons, their dendrites and connections to other neurons, and how their impulses and neurochemicals regulate behavior 7

Functional magnetic resonance imaging (fMRI) –How the human brain responds to food –Response does not occur in the visual cortex (as expected) –Occurs in nucleus accumbens in forebrain Normally involved in reward and pleasure 8

Behavioral Genetics Deals with the contribution that heredity makes to behavior –Nature Obvious that genes guide development of nervous system and potentially the behavioral responses –Nurture Animals may also develop in a rich social environment and have experiences that guide behavior 9

Artificial selection data has shown that behavioral differences among individuals result from genetic differences 10 Behavioral Genetics “maze-bright” versus “maze- dull” groups

Behavioral Genetics Mice fosB gene –Determines whether female mice nurture their young Both fosB alleles disabled = ignore young Normal mothers = protective maternal behavior –Protein expressed by fosB activates other enzymes and genes that affect neural circuitry within the hypothalamus 11

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Learning Altered behavior as a result of previous experiences Nonassociative learning –Does not require an animal to form an association between two stimuli or between a stimulus and response Habituation: decrease in response to a repeated stimulus –No positive or negative consequences 13

Learning Associative learning –Association between two stimuli or between a stimulus and a response Conditioned behavior through association Two major types: –Classical conditioning –Operant conditioning Differ in the way associations are established 14

Learning Associative learning –Paired presentation of two different kinds of stimuli causes the animal to form an association between the stimuli –Toad learns not to eat bumblebee 15

Classical or Pavlovian conditioning –Paired presentation of two different kinds of stimuli with an association formed between them –Meat powder and dogs Unconditioned stimulus: meat Unconditioned response: salivating Conditioned stimulus: bell ringing Conditioned response: after time, the dog salivates with only the ringing of the bell 16 Learning

Operant conditioning –Animal learns to associate its behavior response with a reward or punishment –B.F. Skinner and the Skinner box Rats learned to associate pressing the lever (the behavioral response) with obtaining food (the reward) 17

Learning Instincts govern learning preparedness –Instinct guides learning by determining what type of information can be learned –Learning is possible only within the boundaries set by evolution –Feeding ecology of Clark’s nutcracker (caching seeds to survive the winter) affects the evolution of brain anatomy (an enlarged hippocampus) 18

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Development of Behavior Imprinting –Form social attachment to other individuals or develop preferences that will influence behavior later in life Filial imprinting – attachment between parents and offspring –Konrad Lorenz –1973 Nobel Prize 20

Interactions between parents and offspring are key to the normal development of social behavior –Monkey infant chose cloth mother over wire mother with food –Greater degrees of deprivation of normal social contact in infant monkeys led to greater social behavior abnormalities in childhood and adulthood 21 Development of Behavior

Instinct and learning may interact as behavior develops –White-crowned sparrow males sing species-specific courtship song during mating Genetic template: innate program to learn the appropriate song Cannot learn the song unless they hear it at a critical period in development 22

a. b. Frequency (kHz) Frequency (kHz) Time (s) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24 Some males instinctively know their song Cuckoos are raised by a different species as a brood parasite Development of Behavior

Animal Cognition Do animals show cognitive behavior? –Do they process information and respond in a way that suggests thinking? Chimp shows problem solving to get to suspended banana using boxes Japanese macaques learned to wash sand off potatoes Chimps pull the leaves off of a tree branch to use it as a tool for picking termites Ravens also show problem solving 25

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Orientation and Migratory Behavior Migration – long-range, two-way movements –Each fall, ducks and geese migrate south and return each spring –Monarch butterflies migrate from North America to Mexico May take 2–5 generations 27

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Orientation and Migratory Behavior New population of bobolinks Instead of changing original migration pattern, added a new segment 29

Orientation and Migratory Behavior Migrating animals must be capable of –Orientation – following a bearing –Navigation – ability to set or adjust a bearing May use Sun, stars, Earth’s magnetic field 30

31 Migratory behavior of starlings Navigational abilities of inexperienced birds differ from those of adults that have made the migratory journey before

Animal Communication Successful reproduction depends on appropriate signals and responses –Stimulus–response chain – behavior of one individual releases a behavior by another individual Signals usually highly species- specific 32

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Animal Communication Courtship signals –Flashing of male fireflies recognized by females; female response recognized by males –Provides “check” on species identity of potential mates 34

Animal Communication Pheromones –Chemical messengers used for communication between individuals of the same species Sex attractant Males have sensory receptors Some insect pheromones can be detected as far as 7 km away Acoustic signals –Vocal calls of amphibians or birds 35

Animal Communication Communication facilitates group living –Guards set off an alarm call so group can seek shelter –Social insects produce pheromones that trigger attack behavior –Ants deposit trail pheromones between nest and food source 36

37 Waggle dance of honeybees Animal Communication

Primate language –Vocabulary to communicate identity of specific predators 38

Behavioral Ecology Niko Tinbergen is one of the founders of behavioral ecology Examines the adaptive significance of behavior Natural selection operating on behavior has the potential to produce evolutionary change 39

Behavioral Ecology Tinbergen observed gull nestlings hatch and parents remove the shells of the eggs Placed broken eggs by the nests –Predators (crows) found nests with broken eggs and ate the hatchlings –Nests without egg shells had less predation Concluded that eggshell removal behavior is adaptive: –It reduces predation and thus increases the offspring’s chances of survival 40

Behavioral Ecology Questions asked –Is behavior adaptive? –How is it adaptive? How does it lead to greater reproductive success? Enhance energy intake, increase mating success, decrease predation 41

Behavioral Ecology Foraging behavior can directly influence individual fitness Foraging involves a trade-off between food’s energy content and the cost of obtaining the food Optimal foraging theory: natural selection favors individuals whose foraging behavior is energetically efficient 42

Behavioral Ecology Optimal foraging makes two assumptions 1.Natural selection will favor behavior that maximizes energy acquisition if the increased energy reserves lead to increases in reproductive success – Avoid predators while finding food 2.Optimal behavior has evolved by natural selection Female zebra finches that were successful foraging had successful offspring Removed offspring to ensure learning not a part of the foraging success 43

44 Optimal diet: the shore crab selects a diet of energetically profitable prey Behavioral Ecology

Territorial behavior secures resources –Home range: where the animal lives and forages; defends territory –Defense against intrusion by other individuals –Birds sing or display to signal their territory; energetically costly –Benefit: increased food intake, access to mates, or access to refuges from predators 45

46 Competition for space: territory size in birds is adjusted according to the number of competitors Behavioral Ecology

47 The benefit of territoriality: sunbirds and hummingbirds protect their food source by attacking others that approach flowers in their territory Behavioral Ecology

In some species, exclusive access to females is a more important determinant of territory size for males than food Several females in territory are defended vigorously Nonbreeding season –Male territory size decreases –Aggression decreases 48

Sexual Selection Reproductive strategies –A set of behaviors that presumably have evolved to maximize reproductive succ ess Sexes often have different reproductive strategies –Females do not mate with the first male they encounter –Mate choice: evaluate a male’s quality Peahens mate with males with more eyespots in their tail Frogs mate with males that have complex calls 49

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Sexual Selection Males engage in mate choice less frequently than females Parental investment: contributions each sex makes in producing and rearing offspring –Females have higher investment –Eggs larger than sperm –Females are usually responsible for gestation and lactation, or yolk production Consequences of disparities in reproductive investment – sexes face different selective pressures Females are choosey because it is costly for them to reproduce 51

Sexual Selection In some cases, male investment exceeds that of females –Male Mormon crickets use 30% of their body weight making up a spermatophore for the female –Male seahorses brood and care for the young Females compete for males when males are choosey 52

53 Advantage of male mate choice: male Mormon crickets choose heavier females as mates; larger females have more eggs

Sexual Selection Sexual selection involves both: –Intrasexual selection: interactions between members of one sex –Intersexual selection: interactions between members of opposite sex (mate choice) Sexual selection leads to the evolution of structures used in combat with other males. E.g. Antlers, horns 54

55 Secondary sexual characteristics: horns, long feathers, coloration Sexual Selection

56 Intrasexual selection –Males compete for opportunity to mate –Males defend their territory and females –Dominant males mate with many females: polygyny –Sexual dimorphism: males look different from the females Sexual Selection

Intersexual selection Direct benefits of mate choice –Females benefit by choosing males that help raise offspring –Choose males that provide territories, nesting sites, food Indirect benefits of mate choice –Choose male that is healthiest or oldest –Guppies and birds: coloration reflects quality of diet and health Less likely to carry disease; have good genes –Handicap hypothesis: genetically superior mates can survive a handicap (long tail of the peacock hinders flight) 57

58 Alternative theory to mate choice Sensory exploitation: evolution in males of an attractive signal that “exploits” sound or colors Túngara frog’s chuck sound Sexual Selection Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Frequency (kHz) b Frequency (kHz) c.a. Time (seconds) a: © Michael&Patricia Fogden/Minden Pictures/National Geographic Image Collection

Sexual Selection Mating systems evolved to allow females and males to maximize fitness Mating systems –Monogamy: one male one female –Polygyny: one male many females –Polyandry: one female many males 59

Sexual Selection Option of having more than one mate may be constrained by the need for offspring care –Altricial: offspring require long care Need both parents – monogamy –Precocial: little care required More likely polygynous Polyandrous systems: males usually care for the young, females mate with many males 60

Sexual Selection Extra-pair copulations (EPCs) –Red-winged blackbirds study Half of all nests contained at least one hatchling fertilized by a male other than territory owner –Evolutionary advantage of EPCs Males: increased reproductive success Females: mated with genetically superior individual, even if paired with another male 61

62 The study of paternity. a) DNA fingerprinting gel; b) results of DNA fingerprinting study in red-winged blackbirds Sexual Selection

Alternative mating strategies Fish –Two genetic classes of males Large and small External fertilization: small males “sneak” in to fertilize females Dung beetles –Territorial males have large horns –Small males do not have horns or territories; intercept females in tunnels 63

Altruism Performance of an action that benefits another individual at a cost to the actor Group selection –Selection acting on a population or species –Simply incorrect because individuals that fail to secure mates and not breed will not leave any offspring Seemingly altruistic acts are in fact selfish –Gain parenting experience, inherit territory 64

Altruism Reciprocal altruism: Partnerships in which mutual exchanges of altruistic acts occur because they benefit both participants –Cheaters are discriminated against –Vampire bats Share blood meal 65

Altruism Kin selection –Direct genetic advantage to altruism –Natural selection will favor any behavior, including the sacrifice of life, that increases the propagation of an individual’s alleles –Inclusive fitness – considers gene propagation through direct and indirect reproduction –Hamilton’s rule Altruistic acts are favored when rb > c b and c are benefits and costs, r is the coefficient of relatedness 66

J.B.S. Haldane said he would lay down his life for 2 brothers or 8 first cousins Brothers each had 50% chance of receiving the same allele First cousin would share 1/8 of their alleles 67

Altruism Haplodiploidy Bee hive: eusocial society –single queen lays eggs –Cooperative care of the brood: workers propagate more of their own alleles by giving up their own reproduction to assist their mother in rearing their sisters (75%) –Female workers share 75% of alleles with each sister –Males are haploid –Queen shares 50% of alleles with offspring 68

69 Kin selection in white-fronted bee-eater Males often help others raise their young; helpers usually choose to help close relatives

Social Systems Society: a group of organisms of the same species that are organized in a cooperative manner Advantages –Greater protection from predators –Increase feeding success 70

71 Flocking behavior decreases predation –1011– Number of Pigeons in Flock Reaction Distance (m) Percent Attack Success Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Stuart Westmorland/Getty Images

Social Systems Insect societies include individuals specialized for different tasks Castes: groups of individuals that differ in size and morphology and perform different tasks Workers and soldiers –Honeybees –Leaf-cutter ants 72

Social Systems Vertebrate social systems –Usually less rigidly organized and less cohesive –Diet and predation important in shaping social groups Meerkat sentinel on duty –Naked mole rats are the exception Reproductive division of labor Single “queen” 73