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?