ANIMAL BEHAVIOR

CAMPBELL & REECECHAPTER 51

ANIMAL BEHAVIOR

• a behavior is an action carried out by muscles under control of the nervous system in response to a stimulus

Behavior • over time is subject to natural

selection • understanding any behavior requires

answering 4 ?s1. What stimulus elicits the behavior, & what

physiological mechanisms mediate the response?

2. How does the animal’s experience during growth & development influence the response?

3. How does the behavior aid survival & reproduction?

4. What is the behavior’s evolutionary history?

Behavioral Ecology

• study of the ecological & evolutionary basis for animal behavior

Fixed Action Patterns

• sequence of unlearned acts directly linked to a simple stimulus

• are essentially unchangeable• once started, they continue to

completion• sign stimulus: the trigger for the

behavior

Migration

• a regular long-distance change in location

• animals use environmental stimuli to provide cues to trigger behavior

• some animals track their position relative to the Sun (even though Sun’s position relative to Earth changes thru out the day)

Migration

• animals adjust to changes in Sun’s or stars position by means of circadian clock

• some use magnetic fields (pigeons & some fishes)

Behavioral Rhythms

• linked to seasons called: circannual rhythms– influenced by periods of daylight &

darkness in the environment– birds exposed to artificial light

simulating longer daylight hrs will start to migrate

Behavioral Rhythms

• not all are linked to light/dark–male fiddler crab waves large claw to

attract mates using signal of full or new moon

Animal Signals & Communication

• a stimulus transmitted from 1 animal to another is called a signal

• transmission & reception of signals constitutes animal communication

Forms of Animal Communication

• 4 common modes of animal communication:

1. Visual2. Chemical3. Tactile4. Auditory

Forms of Animal Communication

• courtship behavior of Drosophila melanogaster– is a stimulus-response chain (response

to each stimulus is the stimulus for next behavior

Symbolic Language of the Honeybee

Pheromones

• chemical substances released by animals that communicate thru odors or tastes

• common among mammals & insects• often related to reproductive

behavior

Pheromones as Alarm Signals

• in fish: if 1 injured injured cells release substance that increases vigilance of other fish school becomes more tightly packed move to lake or river bottom where they are safer

Innate Behavior

• animal behavior that is developmentally fixed & under strong genetic control

• it is exhibited in virtually same form in all individuals in a population despite internal & external environmental differences during development & thru out their lifetimes

Experience & Behavior

• How do researchers test the 2nd ?:• How an animal’s experience during

growth & development influence the response to stimuli?

Cross-Fostering Study

• young of 1 species placed under the care of adults from another species

• these studies can be used to measure the influence of social environment & experience on behavior

Human Twin Studies

• compare behaviors of identical twins raised apart with those raised in same household– studies have revealed nature & nuture

both contribute significantly

Learning

• modification of behavior based on specific experiences

Imprinting

• formation at a specific stage in life of a long-lasting behavioral response to a specific individual or object

• distinguished from other types of learning by having a sensitive period or critical period: a limited developmental phase when this type of learning can occur

Imprinting

• during the sensitive period:– the young imprint on their parent &

learn basic behaviors of their species– parents learn to recognize their

offspring

Imprinting

• birds have no innate recognition of “mother”

• they identify with the 1st object they encounter that has certain key characteristics (like any object that is moving away from them)

Greylag Geese Imprinting of Lorenz: 1933

Saving the Whooping Cranes

Spatial Learning

• establishment of a memory that reflects the environment’s spatial structure

• studied digger wasps:–Mother covers entrance with sand when

leaves nest..always comes right back to it

– hypothesized she locates her nest by learning its position relative to local landmarks

Digger Wasp Study

Cognitive Map

• some animals guide their activity using a cognitive map: a representation in the nervous system of the spatial relationships between objects in an animal’s surroundings

• these animals can navigate more flexibly & efficiently by relating landmark positions to one another

Associative Learning

• ability to associate 1 environmental feature (like color) with another (foul taste)

Associative Learning

• suited to lab studies because usually involves classical conditioning or operant conditioning

Classical Conditioning

• an arbitrary stimulus becomes associated with a particular outcome

Operant Conditioning

• aka “trial-and –error” learning

• animal learns to associate one of its behaviors with a reward or punishment & then tends to repeat or avoid that behavior

Associative Learning & Evolution

• makes sense that some animals cannot learn to make particular connections…

• associations animals make typically reflect relationships likely to occur in nature

• associations that cannot be formed are those unlikely to be of selective advantage in a native environment

Cognition

• process of knowing that involves:– awareness– reasoning– recollection– judgement

Cognition

• has been thought that only humans, higher apes & marine mammals

• but...some insects & many other groups of animals have demonstrated some levels of cognition in lab experiments

Problem Solving

• the cognitive activity of devising a method to proceed from 1 state to another in the face of real or apparent obstacles

• varies with individual experience & abilities

Development of Learned Behaviors

• some birds learn their songs in stages (during a sensitive period)– young sparrow does not sing but memorizes

adult songs– followed by a 2nd learning phase when

juvenile bird sings tentative notes called a subsong

– juvenile bird compares his subsong to adult song..when he has it right the song “crystallizes”…bird will only sing that song rest of life

Social Learning

• modification of behavior thru observation of other individuals

• young chimps learn to crack nuts by watching their elders

• young vervet monkeys learn correct use of alarm calls by (+) reinforcement from elders

Social Learning

• forms the roots of culture (a system of information transfer thru social learning or teaching that influences the behavior of individuals in a population)

• can change behavior and thereby influence the fitness of individuals

Foraging Behavior

• food-obtaining behavior• an optimal foraging model is based

on the idea that natural selection should favor the foraging behavior that minimizes the costs of foraging & maximizes the benefits

Mating Behavior & Mate Choice

• mating behavior & mate choice play a major role in determining reproductive success

• includes:– seeking or attracting mates– choosing among potential mates– competing for mates– caring for offspring

Mating Systems

• vary with regard to both the length & # of relationships

• Promiscuous: no strong pair-bonds• Monogamous: mates remain

together for longer periods of time• Polygamous: an individual of one sex

mating with several of the opposite sex

Sexual Dimorphism• extent to which makes & females

differ in appearance– typically varies with type of mating

system–monogamous: male & females alike– polygamous: male much showier than

females

Mating Systems & Parental Care

• needs of the young greatly influences the evolution of mating systems

• young birds require a large amount of food: having a single mom would greatly reduce survival chances…probably why most birds are monogamous

Certainty of Paternity

• influences mating behavior & parental care

• certainty of paternity generally low in most species–may explain why exclusively male

parental care is rare in mammals & birds

Certainty of Paternity

• is high when egg laying & mating occur at same time– external fertilization• fishes: parental care just as likely to be

male parent as female parent

Certainty of Paternity

• does not mean that animals are aware of those factors when they behave a certain way…parental behavior correlates with certainty of paternity because it has been reinforced over generations by natural selection

Sexual Selection

• influences the degree of sexual dimorphism w/in a species

• intersexual selection: 1 sex choose mates on basis of characteristics of other sex– 1 with best song, or dance

• intrasexual selection: competition between members of 1 sex for mates

Mate Choice by Females

• may play central role in evolution of male behavior & anatomy thru intersexual selection

Mate Choice Copying

• behavior in which individuals in a population copy the mate choice of others– female guppies prefer mates that are

ass’c with another female & they prefer male guppies with more orange coloration

Male Competition for Mates

• may involve agonistic behavior: males have a competition..winner gets the female– does not seem to affect genetic

variation

Game Theory

• evaluates alternative strategies in situations where the outcome depends on the strategies of all individuals involved

• provides a way to think about complex evolutionary problems in which relative performance (reproductive success compared to other phenotypes), not absolute performance is the key to understanding evolution of behaviors.

Genetic Basis of Behavior

• studies in insects have revealed existence of regulatory genes that control complex behavior

Courtship Songs of Insects

• found to be under influence of multiple genes as are other specific behaviors– variations in these multiple genes

brings about variation in behavior

Voles Study: Closely Related Species

• single gene variations can determine differences in complex behaviors involved in both mating & parenting– increasing amt of vasopressin receptors

in males changed their mating & parenting behaviors

Genetic Variation & Evolution of Behavior

• significant differences can also be found among members of same species– coastal garter snakes will prey on

banana slugs & inland garter snakes will not a genetically acquired taste

Genetic Variation in Western Garter Snake

• turns out the inland western garter snake cannot detect the odor of the banana slug

• hypothesis: 10,000 yrs ago when garter snake 1st inhabited coastal area those who could smell the plentiful banana slug higher fitness so their #s increased in coastal area

• inland where # of slugs much less, that advantage gone

Variation in Migratory Patterns

• Blackcap warbler: • 1st migratory pattern: Germany

Africa• 1950’s some Germany Britain• behavior change rapid• researchers showed the different

patterns reflected a genetic variation

Altruism

• selflessness• decreases an individual’s fitness but

increases the fitness of others in the population

• explained by concept of inclusive fitness

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

3 Key Variables in Act of Altruism

1. Benefit to the Recipient2. Cost to the Altruist3. Coefficient of Relatedness (r) =

fraction of shared genes• natural selection will favor altruism

when (benefit to recipient) x (r) > (cost to altruist) = Hamilton’s Rule

• altruistic behavior toward unrelated individuals can be adaptive if the aided individual returns the favor in the future

• exchange of favors called reciprical altruism

Sociobiology

• study of how human nature is related to evolutionary behavior

• premise: certain behavioral characteristics exist because they are expressions of genes that have perpetuated by natural selection

• Debate that is ongoing