Lecture 1: Introduction to Animal Behavior & Lecture 2: Ethology

1. Lecture 1: Introduction to Animal Behavior&Lecture 2: Ethology

2. Lecture outline • Introduction to course (schedule, policies, etc…) • Four categories of questions addressed in animal behavior studies • Origins of animal behavior as a field of study • The Ethological approach • Review: Principles of Evolution • Ethological methods • Key concepts in ethology

3. Four categories of questions (Niko Tinbergen, 1963) • What are the mechanisms that cause a behavior? • How does a particular behavior develop (within the individual’s lifetime)? • What is its survival value? (current) • What’s the “working hypothesis”? Is it necessarily true? • Why did it evolve? (past)

4. Origin of animal behavior as a field of study • Ethology • Evolutionary perspective • Primarily field-based • Wide range of animals studied • Psychology • Mechanistic/Developmental perspective • Primarily lab-based • Focused primarily on mammals

5. Ethology: Review of Principles of Evolution • Evolution: Change in the frequency of alleles /genotypes in the population over time (>1 generation) • Adaptation: A phenotypic trait that helps an individual survive/reproduce • Genotype vs. phenotype: What is the difference?

6. Ethology: Review of Principles of Evolution (cont.) • Natural selection: Differential reproduction of genotypes leads to persistence of those genotypes that enable an individual to survive/reproduce most effectively. • Example: Change in antibiotic resistance of the tuberculosis bacterium. • Only traits that are variable and inheritable are subject to natural selection. • Example: Rabbit camouflage • Where does variability come from?

7. Maintenance of non-adaptive traits • Pleiotropy: Multiple effects of a single gene • Linkage: Gene for non-adaptive trait located near gene for highly adaptive trait • Gene flow: Populations in different environments move between habitats, may interbreed • Ex: Funnel-web spiders • Time lag: Non-adaptive traits are being selected against, but are not yet completely gone

8. Ethological methods • Comparative approach • Overall concept: Behavioral differences among related species are due to environmental differences • Example: Comparisons of ground-nesting and cliff-nesting gull species (Esther Cullen, 1957) • NOTE: More details of this study in Signs and Signals video • Benefits of this approach • Be able to explain… • Limitations of this approach • Be able to explain…

9. Ethological methods (cont.) • Experimental approach • Overall concept: manipulate variables in field or lab and observe/measure consequences. • Examples: “Classical” experiments in Signs and Signals video Wednesday (studies by Karl von Frisch, Niko Tinbergen and Konrad Lorenz) • Benefits of this approach • Be able to explain… • Limitations of this approach • Be able to explain…

10. Key concepts in ethology • Fixed action patterns • Can be initiated by environmental stimulus, but proceed to completion • Ex: graylag goose egg-rolling behavior • Occur in unalterable (stereotyped) sequence • Minor alterations may occur • Are not learned (are innate) • Can be triggered inappropriately • Ex: stickleback response to unrealistic models, etc. • Performed by all appropriate members of a species

11. Key concepts in ethology (cont.) • Sign stimuli and releasers • Function: Serve to trigger the FAP • Example: Attack behavior in stickleback males

12. Key concepts in ethology (cont.) • Sign stimuli and releasers (cont.) • Supernormal stimuli • Examples… • Mimicry • Examples… • Role of motivation

13. Key concepts in ethology (cont.) • Chain of reaction • Sequence of events • Example: stickleback courtship • Each behavior of one partner serves as a sign stimulus for the other partner

14. Extension of Evolutionary Theory: Insights into complex behaviors • Optimal strategies: Maximize difference between benefit and cost • Example: TIME SPENT FORAGING • BENEFIT: Gains energy and nutrients • COSTS: • Risk of predation • Energy of dealing with competitors • Energy and time expended in search for and processing food

15. Difficulties of determining and testing what is “optimal”: Must consider how the behavior affects lifetime fitness • But cost/benefit analyses often done in short-term • Easy to run short-term experiments • Various aspects of the behavior converted to manageable units such as “energy” • Often mismatches between short-term and long-term studies. Why?

16. Extension of Evolutionary Theory: Insights into complex behaviors (cont.) • Evolutionarily stable strategies: Two or more strategies may be equivalent in terms of fitness, so that all such strategies are maintained at particular frequencies (proportions) in the population. • Imbalances are self-correcting • Example: Two different strategies of male salmon (Coho, King, Atlantic, others)

17. Description of the two types of males and their different strategies • Costs and benefits of each strategy considered separately • Key: Maximize number of offspring in lifetime! • How the ratios of these strategies are “self-correcting” • What if the proportion of large males increases? • What if the proportion of jacks or precocious par (small males) increases?