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Biology 4101 - Behavioural Ecology
INTRODUCTION
COURSE DESCRUPTION
A course to explore the relationships between animal behaviour
and ecology, emphasizing the behavioural strategies which animals
have evolved to enhance their survival and to increase their
reproductive success. Topics such as foraging, living in groups,
resource defence, sexual selection, parental care, mating systems,
altruism and communication will be discussed within a neoDarwinian framework.
Grading:
Seminar as Seminarian
20%
Seminar as Devil’s Advocate
20%
Midterm
25%
Essay
25%
Participation
10%
TOTAL
100%
Seminar Format:
In any week, seminars will be given by pairs of students based on the paper
that is on the course website.
One pair of students will act as the “Seminarians”, giving the paper, describing
how it was done and what the major conclusions are.
The other pair or students will act as “Devil’s Advocates” and point out flaws
in the paper. Such flaws could be in experimental design, statistical analysis or
the conclusions drawn.
Each pair of students will be given 25 minutes to present their seminar and
then the remaining time will be for discussion. Your contributions to the
discussion period will determine your participation grade. Each pair of
students will present one seminar as the Seminarian and one as the Devil’s
Advocate.
In the first week of class, you must pick a partner and sign up by emailing me
which session you and your partner want to do as the Seminarian and which
you want to do as the Devil’s Advocate. Anyone not signed up by January 10,
2014 will have partners and subjects assigned arbitrarily by me.
BEHAVIOURAL ECOLOGY
ASKING QUESTIONS
Why is it
foraging here?
Is it eating
everything or
being selective?
How does it decide
when to fly back to
the nest?
Does this bird always
forage or does it have
help?
Why is it
foraging alone?
How does it
detect its prey?
Do its own
predators influence
its behaviour?
BEHAVIOURAL ECOLOGY
ASKING QUESTIONS
Why is it
nesting here?
How does it decide
which chicks to feed
first?
Is the work of feeding
shared equally by both
parents?
Why does it have this
number of chicks?
Are all the
chicks related
to the adult?
Why are the
chicks making
so much noise?
Tinbergen’s Four Questions
(The Four Whys)
Why is this bird singing?
1. Causation (physiological explanation)
- sensory/nervous systems
- hormonal systems
- skeleto-muscular system
Niko Tinbergen
(1907 – 1988)
PROXIMATE
FACTORS
2. Development/Ontogeny
- learning, genetic disposition,
developmental mechanisms
3. Adaptive Advantage/Function
- reproductive success
- what are the selective pressures
4. Evolutionary History/Phylogeny
- how song evolved in the bird’s
ancestors
ULTIMATE
FACTORS
UNDERLYING CONCEPTS IN BEHAVIOURAL ECOLOGY
1) Natural Selection (Darwin’s and Genetic)
2) Group vs. Individual Selection
3) Strategies, Costs and Benefits
4) Evolutionarily Stable Strategy
5) Phenotypic Plasticity and Reaction Norms
UNDERLYING CONCEPTS IN BEHAVIOURAL ECOLOGY
1) Natural Selection (Darwin’s formulation)
Observation
1.
2.
All organic populations
can exponentially.
Deduction
1.
In spite of Obs. 1, they
don’t.
There is some kind
of struggle for
existence.
This differential
reproduction/survival is
natural selection
3.
4.
All members of a
species are not the
same.
Differences in
individuals are passed
to their offspring.
2.
Some members of a
species are better
equipped to survive and
reproduce than others.
TOOLS FOR STUDYING BEHAVIOURAL ECOLOGY
1) Natural Selection (modern genetic formulation)
a. All organisms have genes coding for proteins. Proteins, in turn, regulate
development of senses, nervous systems and skeleto-muscular structure.
b. Genes are present in two or more forms (alleles) which code for slight
differences in proteins which, in turn, cause differences in development.
Consequently, there is variation in the population
c. An allele that has more surviving copies of itself and any of its alternatives
will eventually replace those alternatives in the population. Natural selection
is the differential survival of alleles via their effects on reproductive success.
How do genes affect complex behaviour patterns?
Not a clear picture
e.g. melanocortin-1 receptor (MC1R gene)
In lesser snow geese (Anser chen caerulescens):
‘blue’ phase
‘white’ phase
Preferential mating by phase
Mundy et al, 2004. Science 303:1870
How do single genes affect complex behaviour patterns?
Not a clear picture
e.g. melanocortin-1 receptor (MC1R gene)
In rock pocket mouse (Chaetodipus intermedius):
Selective
predation by
owls
Nachman et al, 2003. PNAS 100:5268
How do multiple genes affect complex behaviour patterns?
Black-capped warbler
Sylvia atricapilla
German population - migratory
Canary Islands population
– non-migratory
How do multiple genes affect complex behaviour patterns?
Sylvia atricapilla
Number of half hours with
migratory restlessness
10
German
5
Hybrid
Canary Island
0
50
100
Time (Days)
2) Group vs. Individual Selection
V.B. Wynne Edwards – Group Selection
S
S
S
S
S
S
S
S
S
S
A
S
A
S
S
A
A
S
S
Selfish Population
-overexploits resources
and dies out
A
A
A
A
A
A
A
A
A
A
A
Altruistic Population
-doesn’t overexploit
resources and survives
2) Group vs. Individual Selection
At what level does natural selection operate?
Species of bird
Fledging
Young
Replace
previous?
Genetically determined
1.8
---
Mutant (3 egg)
2.7
Yes
Mutant (4 egg)
3.2
Yes
Can this go on indefinitely?
Number of
fledglings
hatched
Increase in
number of
eggs
Number of
eggs laid
≠
Increase in
number of
offspring
3) Strategies, Costs, and Benefits
Cost –any factor that reduces reproductive
success (directly or indirectly)
Benefit –any factor that increases reproductive
success (directly or indirectly)
Strategy – a set of behavioural courses of action with a
given survival value under a particular set of conditions
In a successful strategy
C < B or
C
<1
B
4) Evolutionarily Stable Strategy (ESS)
An evolutionarily stable strategy is one, if adopted by
all the members of a population cannot be invaded by a
mutant strategy can invade.
John Maynard Smith
(1920-2004)
George R. Price
(1922-1995)
ESS example – Hawk-Dove Game
Hawk - will always fight opponent, may injure opponent or may
be injured
Dove- will never fight opponent.
Payoffs (gains in fitness from a contest)
Winner (Victor)
V = 50
Loser
L=0
Injury Cost
C = -100
ESS example – Hawk-Dove Game
Payoffs (gains in fitness from a contest)
Winner (Victor)
V = 50
Loser L = 0
Injury Cost
C = -100
Assumptions:
1) When Hawk meets Hawk, half of the time it wins, half of the time it’s injured.
2) Hawks always beat Doves.
3) Doves always retreat when meeting a Hawk
4) When Dove meets Dove, the resource is shared
OPPONENT
Hawk
Hawk
½ V - ½ C = -25
Dove
V = 50
ATTACKER
Dove
L=0
½ V = 25
ESS example – Hawk-Dove Game
Is either strategy an ESS?
Mutant Dove strategy
If population is all Hawks
NOT AN ESS
Payoff/contest = -25
Payoff/contest = 0
Mutant Hawk strategy
If population is all Doves
NOT AN ESS
Payoff/contest = 25
Payoff/contest = 50
5) Phenotypic Plasticity and Reaction Norms
Parus major – over 47 years – first egg laying date advanced by 14 days
Hypotheses
1) Response to environmental cues?
2) Microevolutionary change?
5) Phenotypic Plasticity and Reaction Norms
Hypotheses
1) Response to environmental cues?
✔
2) Microevolutionary change?
Reaction norm – if phenotypic variation is continuous, the relationship
between the phenotype and the environment for each genotype.
5) Phenotypic Plasticity and Reaction Norms
Britain
The Netherlands
Reaction norm – if phenotypic variation is continuous, the relationship
between the phenotype and the environment for each genotype.
Next time – Hypothesis Testing and Foraging Economics