Lecture 1: Lecture 1: Introduction to Introduction to

Animal BehaviorAnimal Behavior

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Lecture 2: EthologyLecture 2: Ethology

Lecture outlineLecture outline

1.1. Introduction to course Introduction to course (schedule, (schedule, policies, etc…)policies, etc…)

2.2. Four categories of questions Four categories of questions addressed in animal behavior addressed in animal behavior studiesstudies

3.3. Origins of animal behaviorOrigins of animal behavior as a as a field of studyfield of study

4.4. The Ethological approachThe Ethological approach• Review: Principles of EvolutionReview: Principles of Evolution• Ethological methodsEthological methods• Key concepts in ethologyKey concepts in ethology

Four categories of questions Four categories of questions (Niko Tinbergen, 1963)(Niko Tinbergen, 1963)

What are the mechanisms that What are the mechanisms that cause a behavior?cause a behavior?

How does a particular behavior How does a particular behavior develop (within the individual’s develop (within the individual’s lifetime)?lifetime)?

What is its survival value? (current)What is its survival value? (current) What’s the “working hypothesis”? Is it necessarily What’s the “working hypothesis”? Is it necessarily

true?true?

Why did it evolve? (past)Why did it evolve? (past)

Origin of animal behavior as Origin of animal behavior as a field of studya field of study

EthologyEthologyEvolutionary perspectiveEvolutionary perspectivePrimarily field-basedPrimarily field-basedWide range of animals studiedWide range of animals studied

PsychologyPsychologyMechanistic/Developmental perspectiveMechanistic/Developmental perspectivePrimarily lab-basedPrimarily lab-basedFocused primarily on mammalsFocused primarily on mammals

Ethology: Review of Ethology: Review of Principles of EvolutionPrinciples of Evolution

Evolution: Evolution: Change in the frequency Change in the frequency of of allelesalleles / /genotypesgenotypes in the in the population over time (>1 generation)population over time (>1 generation)

Adaptation: Adaptation: A A phenotypicphenotypic trait that trait that helps an individual survive/reproducehelps an individual survive/reproduce

Genotype vs. phenotype: Genotype vs. phenotype: What is What is the difference?the difference?

Ethology: Review of Ethology: Review of Principles of Evolution Principles of Evolution

(cont.)(cont.) Natural selection: Natural selection: Differential Differential

reproduction of genotypes leads to reproduction of genotypes leads to persistence of those genotypes that enable persistence of those genotypes that enable an individual to survive/reproduce most an individual to survive/reproduce most effectively.effectively. Example: Change in antibiotic resistance of the Example: Change in antibiotic resistance of the

tuberculosis bacterium.tuberculosis bacterium. Only traits that are variable and Only traits that are variable and

inheritableinheritable are subject to natural selection. are subject to natural selection. Example: Rabbit camouflageExample: Rabbit camouflage

Where does variability come from?Where does variability come from?

Maintenance of non-adaptive Maintenance of non-adaptive traitstraits

Pleiotropy: Pleiotropy: Multiple effects of a single geneMultiple effects of a single gene Linkage: Linkage: Gene for non-adaptive trait Gene for non-adaptive trait

located near gene for highly adaptive traitlocated near gene for highly adaptive trait Gene flow: Gene flow: Populations in different Populations in different

environments move between habitats, may environments move between habitats, may interbreedinterbreed Ex: Funnel-web spidersEx: Funnel-web spiders

Time lag: Time lag: Non-adaptive traits are being Non-adaptive traits are being selected against, but are not yet completely selected against, but are not yet completely gonegone

Ethological methodsEthological methods

Comparative approachComparative approach Overall conceptOverall concept: Behavioral differences : Behavioral differences

among related species are due to among related species are due to environmental differencesenvironmental differences

Example: Comparisons of ground-nesting and cliff-Example: Comparisons of ground-nesting and cliff-nesting gull species (Esther Cullen, 1957)nesting gull species (Esther Cullen, 1957)

NOTE: More details of this study in Signs and Signals NOTE: More details of this study in Signs and Signals videovideo

Benefits of this approach Benefits of this approach Be able to explain…Be able to explain…

Limitations of this approachLimitations of this approachBe able to explain…Be able to explain…

Ethological methods Ethological methods (cont.)(cont.)

Experimental approachExperimental approach Overall conceptOverall concept: manipulate variables in : manipulate variables in

field or lab and observe/measure field or lab and observe/measure consequences.consequences.

Examples: “Classical” experiments in Signs and Examples: “Classical” experiments in Signs and Signals video Wednesday (studies by Karl von Frisch, Signals video Wednesday (studies by Karl von Frisch, Niko Tinbergen and Konrad Lorenz)Niko Tinbergen and Konrad Lorenz)

Benefits of this approach Benefits of this approach Be able to explain…Be able to explain…

Limitations of this approachLimitations of this approachBe able to explain…Be able to explain…

Key concepts in ethologyKey concepts in ethologyFixed action patternsFixed action patterns

Can be initiated by environmental Can be initiated by environmental stimulus, but proceed to completionstimulus, but proceed to completionEx: graylag goose egg-rolling behaviorEx: graylag goose egg-rolling behavior

Occur in unalterable (stereotyped) Occur in unalterable (stereotyped) sequencesequenceMinor alterations may occurMinor alterations may occur

Are not learned (are innate)Are not learned (are innate)Can be triggered inappropriatelyCan be triggered inappropriately

Ex: stickleback response to unrealistic models, Ex: stickleback response to unrealistic models, etc.etc.

Performed by all appropriate members of Performed by all appropriate members of a speciesa species

Key concepts in ethology Key concepts in ethology (cont.)(cont.)

Sign stimuli and releasersSign stimuli and releasers Function: Serve to trigger the FAPFunction: Serve to trigger the FAP

Example: Attack behavior in stickleback malesExample: Attack behavior in stickleback males

Key concepts in ethology Key concepts in ethology (cont.)(cont.)

Sign stimuli and releasers (cont.)Sign stimuli and releasers (cont.)Supernormal stimuliSupernormal stimuli

Examples…Examples…MimicryMimicry

Examples…Examples…Role of motivationRole of motivation

Key concepts in ethology Key concepts in ethology (cont.)(cont.)

Chain of reactionChain of reactionSequence of eventsSequence of eventsExample: stickleback Example: stickleback

courtshipcourtshipEach behavior of one Each behavior of one

partner serves as a sign partner serves as a sign stimulus for the other stimulus for the other partnerpartner

Extension of Evolutionary Theory: Extension of Evolutionary Theory: Insights into complex behaviorsInsights into complex behaviors

Optimal strategies: Optimal strategies: Maximize difference Maximize difference between benefit and costbetween benefit and cost

Example: TIME SPENT Example: TIME SPENT FORAGINGFORAGING

BENEFITBENEFIT: Gains energy : Gains energy and nutrients and nutrients

COSTSCOSTS: : • Risk of predationRisk of predation• Energy of dealing with Energy of dealing with competitorscompetitors• Energy and time Energy and time expended in search for expended in search for and processing foodand processing food

Difficulties of determining and Difficulties of determining and testing what is “optimal”: testing what is “optimal”: Must Must consider how the behavior affects consider how the behavior affects lifetime fitnesslifetime fitnessBut cost/benefit analyses often done in But cost/benefit analyses often done in

short-termshort-termEasy to run short-term experimentsEasy to run short-term experimentsVarious aspects of the behavior converted to Various aspects of the behavior converted to

manageable units such as “energy”manageable units such as “energy”Often mismatches between short-term Often mismatches between short-term

and long-term studies. Why?and long-term studies. Why?

Extension of Evolutionary Theory: Extension of Evolutionary Theory: Insights into complex behaviors Insights into complex behaviors

(cont.)(cont.)Evolutionarily stable strategies: Evolutionarily stable strategies:

Two or more strategies may be Two or more strategies may be equivalent in terms of fitness, so that equivalent in terms of fitness, so that all such strategies are maintained at all such strategies are maintained at particular frequenciesparticular frequencies (proportions) in (proportions) in the population.the population.Imbalances are self-correctingImbalances are self-correctingExample: Two different strategies of male Example: Two different strategies of male

salmon (Coho, King, Atlantic, others)salmon (Coho, King, Atlantic, others)

Description of the two types of Description of the two types of males and their different strategiesmales and their different strategies

Costs and benefits of each strategy Costs and benefits of each strategy considered separatelyconsidered separatelyKey: Maximize number of offspring in Key: Maximize number of offspring in

lifetime!lifetime!How the ratios of these strategies How the ratios of these strategies

are “self-correcting”are “self-correcting”What if the proportion of large males What if the proportion of large males

increases?increases?What if the proportion of jacks or precocious What if the proportion of jacks or precocious

par (small males) increases?par (small males) increases?