Behavioral Biology Chapter 54

Approaches Behavior: the way an animal responds to stimulus in its environment Two components of behavior Immediate cause Evolutionary origin Proximate causation:“how” of behavior Measure: hormone level - testosterone Impulse of nerve signal

Approaches Ultimate causation: “why” of behavior Determine how behavior influences reproductive success or survival Controversy: Is behavior determined by individual’s genes Or by learning and experience Nature or nurture

Approaches Innate behavior: instinctive, does not require learning Preset paths in nervous system Genetic: fixed action pattern Example: goose replacing an egg from her nest

Approaches Egg retrieval behavior is triggered by a sign stimulus Innate releasing mechanism or fixed action pattern is the stereotyped act Not very specific: anything round will trigger the goose’s reaction Once pattern begins, it goes to completion; even if the egg is removed

Approaches Male stickleback fish will attack anything with a red underside Does not need to be a fish Supernormal stimuli: given a choice: animals respond to a larger stimuli over a normal size stimuli

Behavioral Genetics Artificial selection data has shown that behavioral differences among individuals often result from genetic differences Genetics of learning

Behavioral Genetics Human twin study Identical twins: identical genetically 50 sets, twins raised separately Similarity in personality, temperament, leisure time activities Indicates that genetics plays a role in determining behavior even in humans

Behavioral Genetics Single gene: Drosophila Alternative alleles for feeding behavior as larvae One type moves around to eat Second type remain in same area to eat Courtship behavior also affected by a mutation in a single gene

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

Behavioral Genetics fosB present: mother cares for her young fosB absent: young are ignored and eventually die

Behavioral Genetics Prairie voles are monogamous Montane voles mate and do not work together to raise young Different response to oxytocin and vasopressin Peptide receptors different

Learning 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

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

Learning Associative learning is involved in predator-prey interactions: after being stung the toad learns not to eat bumblebees.

Classical conditioning: the paired presentation of two different kinds of stimuli with an association formed between them Pavlovian conditioning Unconditioned stimulus: meat Unconditioned response: salivating Conditioned stimulus: bell ringing Conditioned response: After time, the dog salivates with only the ringing of the bell

Learning Operant conditioning: animal learns to associate its behavior response with a reward or punishment B.F. Skinner Trial and error learning Today it is believed that instinct guides learning by determining what type of information can be learned through conditioning

Learning Instinct and learning Innate predispositions toward forming certain associations Pigeons can learn to associate food with colors, but not with sound Learning is possible only within the boundaries set by instinct In nature, adaptation by learning is important to survival

Learning Clark’s nutcracker can remember the locations of up to 2000 seed caches months after hiding them Uses spatial memory

Development of Behavior Parent-offspring interactions influence cognition and behavior Imprinting: formation of social attachment to other individuals or develop preferences that will influence behavior later in life Filial imprinting: attachment between parents and offspring Konrad Lorenz

Development of Behavior Goslings follow Konrad Lorenz as if he were their mother 1973 Nobel Prize

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 Can not learn the song unless they hear it at a critical period in development

Development of Behavior Exposed to own species song during development Not exposed to song

Development of Behavior Cuckoos are raised by a different species Learn their own song: innate

Animal Cognition Do animals show cognitive behavior What type of behavior demonstrates cognition? Japanese macaques learned to wash sand off potatoes Chimps pull the leaves of off a tree branch to use it as a tool for picking termites Some birds learn to take off milk caps from bottles

Animal Cognition

Orientation and Migratory Behavior Orientation: goal-oriented movements Track stimuli in the environment Homing instinct Taxis: movement toward or away from a stimulus Kineses: more or less active when stimulus intensity increases

Orientation and Migratory Behavior Migration involves population moving large distances Monarch butterflies fly from North America to Mexico

Orientation and Migratory Behavior It takes 2 - 5 generations for the migration

Orientation and Migratory Behavior Bobolinks have changed their migration by adding a new segment

Orientation and Migratory Behavior Migrating animals must be capable of orientation and navigation Navigation: the ability to set or adjust a bearing Sun and stars: general direction Earth’s magnetic field: specific path Information from the stars overrides the magnetic information if they conflict

Orientation and Migratory Behavior Migratory behavior of starlings

Communication Communication can play a key role in behaviors Among members of the same species Between species Successful reproduction depends on appropriate signals and responses Stimulus-response chain: behavior of one individual releases a behavior by another individual

Communication Long-distance communication Pheromones: chemical messengers Sex attractant Males have sensory receptors Some insect pheromones can be detected as far as 7km away Acoustic signals Vocal calls, wing clicking Light signals: firefly

Communication Bioluminescent displays of lampyrid beetles are species-specific. Each number represents the flash pattern of a male of a different species

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

The waggle dance of honeybees Communication The waggle dance of honeybees

Communication James L. Gould devised an experiment to trick hive members into going in the wrong direction Supported von Frisch’s explanation of the bees using the Sun as their reference position Eliminated Wenner’s challenge that it was flower odor that drew the bees to the food location Robot bees are now being used

Communication Primate language: Vocabulary to communicate identity of specific predators

Communication Chimpanzees and gorillas can learn to recognize a large number of symbols and use them to communicate abstract concepts Complexity of human language Differences are superficial 3000 languages draw from the same set of 40 consonant sounds

Communication Signals vary in their degree of specificity Level of specificity: relates to the function of a signal Mark territories with pheromones Species and other species specific Pursuit-deterrent signals: predator has been seen and should not waste time chasing the prey

Communication Cleaner Fish. The grouper has entered the cleaner fish’s “station” and adopted a posture that allows the cleaner fish to enter the mouth and gills and feed on attached parasites

Behavioral Ecology Niko Tinbergen divided the investigation of behavior into the study of Development Physiological basis Function: including evolutionary significance

Behavioral Ecology Evolutionary analysis: survival value of behavior 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

Behavioral Ecology Behavioral ecology: study of how natural selection shapes behavior Adaptive significance of behavior Reproductive success, fitness Questions asked Is behavior adaptive How is it adaptive Enhance energy intake, increase mating success, decrease predation

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

Optimal foraging makes two assumptions Behavioral Ecology Optimal foraging makes two assumptions Natural selection will only favor behavior that maximizes energy acquisition if the increased energy reserves lead to increases in reproductive success Avoid predators Find mates

Behavioral Ecology 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

Behavioral Ecology 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

Behavioral Ecology Competition for space. Territory size in birds is adjusted according to the number of competitors

Behavioral Ecology 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

Sexual Selection Reproductive strategies: decisions about mating How many mates to have How much time devoted to rearing offspring How much energy devoted to rearing offspring Evolved partly in response to cost of reproduction

Sexual Selection 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

Sexual Selection Products of sexual selection. Attracting mates with long feathers is common in bird species

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

Sexual Selection Consequences of disparities in reproductive investment - sexes face different selective pressures Male fitness rarely limited by sperm count Number of eggs produced often does limit reproductive success Females are choosey because it is costly for them to reproduce

Sexual Selection Advantage of male mate choice. Male Mormon crickets choose heavier females as mates, larger females have more eggs

Sexual Selection 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

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. Ex. Antlers, horns

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

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

Sexual Selection Sperm competition Females mate with multiple males Males evolved features to maximize sperm success Testes large to produce many sperm per mating Sperm large and swim more rapidly

Sexual Selection Intersexual selection Direct benefits of mate choice Females benefit by choosing males that help raise offspring Males that do not help raise young; provide territories, nesting sites, food, predator refuges

Sexual Selection 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 Good genes Handicap hypothesis: genetically superior mates can survive a handicap

Sexual Selection Alternative Theory Sensory exploitation: evolution in males of an attractive signal that “exploits” sound or colors Túngara frog Cluck sound

Sexual Selection Mating systems reflect adaptations for reproductive success Energy costs, food resources, nest sites, distribution of opposite sex Mating systems Monogamy: one male one female Polygyny: one male many females Polyandry: one female many males

Sexual Selection Mating systems influenced by ecology Territory size Needs of offspring Both parents: monogamy Altricial: offspring require long care Precocial: little care required Polyandrous systems: males usually care for the young, females mate with many males

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

Sexual Selection Extra-pair copulations (EPCs) Red-winged blackbirds study Half of all nests contained at least one hatchling fertilized b a male not defending the territory Evolutionary advantage of EPCs: Males: increased reproductive success Females: genetically superior individual mated with, even if paired with another male

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

Male fish fertilizing a female’s eggs Sexual Selection Male fish fertilizing a female’s eggs

Altruism Altruism: the performance of an action that benefits another individual at a cost to the actor Question: if altruism imposes a cost to an individual, how could an allele be favored by natural selection? Group selection: rare Among groups: leads to a decrease in allele’s frequency Within groups: may favor the allele

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

Altruism Kin selection: direct genetic advantage; selection favors relatives William Hamilton: explanation in 1964 Brothers: 50% of alleles First cousin: 1/8th of alleles Hamiltons’s rule: altruistic acts are favored when rb > c b and c are benefits and costs, r is the coefficient of relatedness

Altruism

Altruism Kin selection in white-fronted bee-eater

Altruism Haplodiploidy and Hymenopteran social evolution Bee hive: eusocial society single queen lays eggs 50,000 workers, no 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%)

Reproductive division of labor in honeybees Altruism Reproductive division of labor in honeybees Female workers share 75% of alleles with each sister Males are haploid Queen shares 50% of alleles with offspring

Social Systems Society: a group of organisms of the same species that are organized in a cooperative manner Advantages Kin selection: greater odds of alleles surviving in the gene pool Greater protection from predators Increase feeding and mating success

Flocking behavior decreases predation Social Systems Flocking behavior decreases predation

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 Fire ants

Social Systems Foraging and predator avoidance Meerkat sentinel on duty Take turns to act as lookout