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Lecture 1: Introduction to Animal Behavior & Lecture 2: Ethology Lecture outline 1. Introduction to course (schedule, policies, etc…) 2. Four categories of questions addressed in animal behavior studies 3. Origins of animal behavior as a field of study 4. The Ethological approach • • • Review: Principles of Evolution Ethological methods Key concepts in ethology 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 true? the “working hypothesis”? Is it necessarily Why did it evolve? (past) Origin of animal behavior as a field of study Ethology Evolutionary perspective Primarily field-based Wide range of animals studied Psychology Mechanistic/Developmental Primarily perspective lab-based Focused primarily on mammals 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? 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? 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 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… 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… Key concepts in ethology Fixed action patterns Can be initiated by environmental stimulus, but proceed to completion Ex: Occur graylag goose egg-rolling behavior 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 species by all appropriate members of a Key concepts in ethology (cont.) Sign stimuli and releasers Function: Serve to trigger the FAP Example: Attack behavior in stickleback males Key concepts in ethology (cont.) Sign stimuli and releasers (cont.) Supernormal stimuli Examples… Mimicry Examples… Role of motivation 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 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 Difficulties of determining and testing what is “optimal”: Must consider how the behavior affects lifetime fitness But cost/benefit analyses often done in shortterm 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? 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) 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?