Transcript Lecture 1: Introduction to Animal Behavior

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?