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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
 What is its survival value? (current)
 What’s
the “working hypothesis”? Is it necessarily
Why did it evolve? (past)
Origin of animal behavior as a
field of study
Primarily field-based
Wide range of animals studied
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
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
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
 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
be initiated by environmental stimulus,
but proceed to completion
 Ex:
graylag goose egg-rolling behavior
in unalterable (stereotyped) sequence
 Minor
alterations may occur
not learned (are innate)
Can be triggered inappropriately
 Ex:
stickleback response to unrealistic models, etc.
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.)
 Examples…
 Examples…
of motivation
Key concepts in ethology (cont.)
Chain of reaction
of events
Example: stickleback
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
BENEFIT: Gains energy
and nutrients
• Risk of predation
• Energy of dealing with
• 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
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”
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.
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
Maximize number of offspring in lifetime!
How the ratios of these strategies are
if the proportion of large males
What if the proportion of jacks or precocious
par (small males) increases?