Transcript Behavioral Ecology - College of Forestry, University of Guangxi

Lecture 5:
Behavioral Ecology
Principles of Ecology
Eben Goodale…
Guest Lecturer: Uromi Goodale
College of Forestry, Guangxi University
Today’s lecture
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4 questions of behavioral ecology
Nature vs. nurture
Foraging ecology
Charles Darwin’s two biggest problems:
– Sexual Selection
– Group Living and Altruism.
• Looking at human behavior
Why did the prize for physiology（生理学） /
medicine go to these three men?
Konrad Lorenz
(1903-1989)
ducks imprint on
（被铭记为）
human “parents”
Niko Tinbergen
(1907-1988)
Worked on stimuli
（刺激） that
“release” behavior
Karl Von Frisch
(1886-1982)
Discovered honeybee
“dance language”
Nobel prize 1973: study of behavior as a physiological process
Tinbergen’s four questions
• What stimulus elicits the behavior,
and what physiological mechanisms
mediate the response?
• How does the animal’s experience
during growth and development
influence the response?
• How does the behavior aid survival
and reproduction?
• What is the behavior’s evolutionary
history?
Tinbergen’s four questions
• What stimulus elicits the behavior, and what
physiological mechanisms mediate the
response? Mechanistic（机械的）
• How does the animal’s experience during
growth and development influence the
response? Developmental（发展的）
• How does the behavior aid survival and
reproduction? Ultimate Function
• What is the behavior’s evolutionary history?
Evolutionary history（进化历史）
Nature versus nurture: the debate
• Ethologists (like
Tinbergen) see
strong innate（先天
的） responses.
• Psychologists (like B.
F. Skinner) see
everything can be
learned.
The super-stimulus: an incubating bird,
given an extra big egg, will try to sit on it.
Genetically innate. Cuckoos take advantage.
The ‘Skinner box’: demonstration that by
reinforcing ‘correct’ behavior with food, pigeons
can be taught to do complex tasks.
So nature（自然的） vs. nurture（后天培养
的）: 2 camps.
Is there a middle ground?
Square on a flat surface: experience (the landscape) has no effect,
Innate effects rule…wherever the square lands it stays.
So nature vs. nurture: 2 camps.
Is there a middle ground?
Circle on a flat surface: circle can roll in any direction… experience rules.
So nature vs. nurture: 2 camps.
Is there a middle ground?
Circle on a surface with a channel: there’s room to roll (= room for
experience), but some places more likely than others.
Channeled learning（引导学习）:
rats
• Rats learning to associate bad smells to avoid
foods.
• But can’t learn to associate sound to avoid
foods (but dogs can).
Conclusion: all behavior a mix of
genetically innate and learned components.
It’s a continuum（连续的).
Some behaviors mostly innate.
Think of any human examples?
Some behaviors mostly leaned.
Today’s lecture
•
•
•
•
4 questions of behavioral ecology
Nature vs. nurture
Foraging ecology
Charles Darwin’s two biggest problems:
– Sexual Selection
– Group Living and Altruism.
• Looking at human behavior
Foraging ecology
• Do animals behave in a way
that maximizes the amount
of energy that they obtain?
• “Optimal foraging ecology
（最佳环境容量)”
• What prey do animals select?
• How long do they stay in one
patch before moving to the
next one?
• How do they forage to use
the least energy needed to
obtain food?
John Krebs tested birds
on what prey they would
select as it came by on a belt.
Prey selection:
minimizing “handling time（处理时间)”
• The profitability（利
益率) of food =
E / t (Energy/time)
• Look at this
experimentally by
having different kinds
of “prey” that are
easier of harder to
obtain (glue or tape)
From Krebs et al. 1977
Minimizing travel:
when to leave a patch?
• When a patch（斑点）
is first found, it has a
lot of food, and
feeding is quick.
• But it becomes less
rich over time.
• The animal also
needs to consider the
energy required to
find a new patch.
The longer the travel time between patches,
the longer the animal will stay in one patch.
From Cowrie 1977
Ultimate function and Optimality Theory
• An example … Crows drop whelks (snail in
shell) against the ground.
• Higher they go, the more successful … but the
more time it takes. How high should they go?
Zach (1978, 1979)
The field evidence:
Crows select largest whelks
Crows drop whelks from ~ 5 m
Minimizing energy spent:
how to crack a shell
N = Number of drops
H = height
Energy
spent
Height
Crows end up going about as high as this model predicts (~ 2 m)
Crows are such smart, cool birds:
http://www.thewildclassroom.com/biodiversity/birds/aviantopics/optimalforagingtheory.html
But do animals really
behave optimally?
• “Optimal foraging
ecology” peaks in late
1970s.
• People begin to realize
that birds not
following predictions
particularly: when
predators are present,
when information is
not perfect, where
results are variable etc.
Today’s lecture
•
•
•
•
4 questions of behavioral ecology
Nature vs. nurture
Foraging ecology
Charles Darwin’s two biggest problems:
– Sexual Selection
– Group Living and Altruism.
• Looking at human behavior
Darwin’s Problems
• Two difficult problems:
– Sexual selection（性选择）
Why do some animals have
very elaborate ornaments
that may be costly to their
survival?
– Altruism（偏利作用）
Why do organisms help
others at a cost to
themselves?
Worried Darwin. These are both
potentially large problems for his
theory of natural selection.
These honeybee
Workers help their
queen but don’t
reproduce themselves
Darwin’s Problems
• Two difficult problems:
– Sexual selection
Why do some animals have
very elaborate ornaments
that may be costly to their
survival?
– Altruism
Why do organisms help
others at a cost to
themselves?
Worried Darwin. These are both
potentially large problems for his
theory of natural selection.
1859
Origin of Species
1871
Descent of Man and
Selection in Relation
To Sex
Natural selection
What are the basic steps in this process:
1. Variation between individuals in traits
2. This variation is the trait is heritable
3. In every generation, there are more
offspring produced than can survive.
4. Individuals with traits that fit the
environment well survive and reproduce.
5. More individuals in the next generation will
have the favored trait.
Sexual selection
What are the basic steps in this process:
1. Variation between individuals in traits
2. This variation is the trait is heritable
3. The trait in question affects the individual’s
ability to mate. Individuals with traits that
attract mates or beat rivals will leave more
offspring.
4. More individuals in the next generation will
have the favored trait.
Natural selection and sexual selection
collide
Ever see a male peacock fly?
With difficulty! How can we understand this from a
Darwinian perspective….?
Sexual selection
Intrasexual（性内的）
Two male elephant seals fight for access to females
Intersexual
A male sage-grouse displays for females
Are females really using male
ornaments to select mates?
Famous experiment: Andersson 1982
Control I is unmanipulated birds. What is Control II and why do it?
Idea of differences
between sexes in investment in offspring
Females produce a few, costly gametes（配子 – eggs
Males produce many inexpensive gametes – sperm
For females to reproduce, make best use of a few attempts
Parental
Investment
Theory
Formalized by
Robert Trivers
(1972)
Male success can come from reproducing many times
Females “choosy（挑剔的）” …note this is a generalization,
not always true
Some exceptions prove the rule about
investment
• General idea that female
invest more per one
offspring, so should be
more choosy.
• In species where males
invest more, females are
more colorful, fight; and
males choose.
In Jacanas, females mate with
more than one male. Kill offspring
male has with other females.
In Pharalopes, males incubate
Eggs; females brighter plumage
In pipefish, males get pregnant
Males choose females.
Sexual selection: benefits for females
What does the female (or in exceptional cases, the male) stand
to gain by choosing good quality males (females)?
Direct benefits: female gets nutrition or help rearing young
Scorpion Fly:
male gives the
female a “nuptial
gift” before
meeting
Sexual selection: benefits for females
• Direct benefits very important for animals
where a lot of parental care is necessary…
Like birds where both
parents are needed to
feed chicks (“altricial
young（成雏期)”)…
But what about those lekking birds??
The males provide no parental genes.
All they do is show off.
http://www.youtube.com/watch?v=uVSxEkCU
Ag0&feature=related
What about the male peacocks that Petrie 1994 writes about?
How do females benefit from selecting well-ornamented males?
Sexual selection
• So why would a female chose a male when
parenting skills are not an issue?
The “sexy son（性感儿子）” hypothesis:
female choses male in hopes that her
own male offspring will be attractive to
females.
The “good genes（优良基因）” /
“handicap（阻碍）” hypothesis: A male
peacock is announcing through his
feathers, “I’m in such good condition
and have such good genes that I can
survive despite this ridiculous (crazy)
tail”.
Amotz Zahavi (1928-)
Sexual selection
• So why would a female chose a male when
parenting skills are not an issue?
Problem with these theories… why
wouldn’t all males evolve to the same
appearance (i.e., their phenotype) … why
wouldn’t we run out of genetic variation?
One solution: appearance is an indicator of
resistance to pathogens（病原体） or parasites
（寄生虫）. Pathogens/parasites are constantly
changing, so appearance can be an honest
signal of genetic quality.
Idea propounded
By Marlene Zuk
At UCRiverside
(1956- )
Sexual selection
And may be there isn’t
an adaptive reason…
Ronald Fisher
hypothesized that if
male and female sexual
preference was
genetically linked, males
could evolve more of
trait at same time
females evolve
preference for it
Their sons have
longer tail
Males
with long
tail successful
Their daughters
really like
long tails
This process, called “run-away（逃跑者）” sexual selection,
might lead to a cycle of trait elaboration.
Sexual selection
Stalk-eyed flies: evidence that female preference（优先权）
evolves at same time as male trait. Wilkonson and Reillo 1994
Today’s lecture
•
•
•
•
4 questions of behavioral ecology
Nature vs. nurture
Foraging ecology
Charles Darwin’s two biggest problems:
– Sexual Selection
– Group Living and Altruism.
• Looking at human behavior
Types of Animal Groups
• Non-related: groups at a
scarce resource: incidental
groups (aggregations（聚
集）)
• Non-related groups: herds,
flocks, schools, swarms…
• Related groups: colonies
(bees, ants), family groups
of animals (cooperative
breeding birds)…..
The selfish herd
Start with non-related groups:
individuals should join them to
reduce their own risk
“Geometry for the Selfish Herd”
W. D. Hamilton (1971)
1) Marginal animals
more vulnerable（脆
弱）.
2) Animals move
towards middle of
group.
Benefits/costs to groups: predation
（捕食）
• Vigilance （警觉）
• Dilution of risk（降低
风险）
• Confusion effect
• Threaten predator
…. But costs
• More obvious to
predators
1 2 4 8 12
1 2 4 8 12
Group Size
Vigilance by skinks: Downes and Hoefer 2004
Benefits/costs to groups: foraging
• Hidden food found more
easily due to copying
• Disturbance of food
But costs…
• Increased competition
• Aggression or
Kleptoparasitism (stealing)
#
Birds
% of birds find
food in 15 min
1
25%
2
40%
4
75%
Krebs et al. 1972
Group size … what’s optimal（最理想
的）?
Factors
Increasing
Group Size:
Factors
Decreasing
Group Size:
Vigilance,
increased
feeding
Aggression
Caraco 1980
Group size … what’s optimal?
Daily
survival
rate
Dail
Covey size
Quail coveys: Williams (2003)
Cooperative breeders
Now let’s talk about special kinds of groups
in which the members are related.
In cooperative breeders
（繁殖）,
Only one male and one
female breed, whereas
others (usually juveniles
（小的）) help raise young.
Green wood-hoopoes
Why do the helpers help?
Kin selection = an explanation for
altruism
W. D. Hamilton (1936-2006)
suggested that “altruistic” behaviors
could be explained as an
animal helping closely related
individuals, and thereby perpetuating
their genes.
This is known as “kin selection”.
Kin selection
Hamilton’s rule:
rB – C > 0
mate
r = Relatedness
B = Benefit
C = Cost of helping
How do we calculate r?
For diploid（二倍体） organisms,
You get ½ your alleles
From mother, ½ from father.
r = is percent of
genes that are shared
children
Kin selection
Hamilton’s rule:
rB – C > 0
mate
r = Relatedness
B = Benefit
C = Cost of helping
How do we calculate r?
For diploid organisms,
You get ½ your alleles
From mother, ½ from father.
What is r for
Mother and daughter?
50%
children
Kin selection
Hamilton’s rule:
rB – C > 0
mate
r = Relatedness
B = Benefit
C = Cost of helping
How do we calculate r?
For diploid organisms,
You get ½ your alleles
From mother, ½ from father.
What is r for 2 sisters?
100 + 50 + 50 + 0 / 4 = 50%
children
Cooperative（协同） behavior
Why do the helpers help?
They stay because by helping raise
Their kin, they are increasing their
Genes in the next generation.
Lion pride: Males only form
group of 3 or more if related…
Eusocial animals
What characteristics do eusocial（社会性的） animals have?
1) Individuals of more than one generation living together
2) cooperative care of young
3) division of individuals into non-reproductive and
reproductive castes
Naked mole rat
Leaf cutter ant queen
How did eusocial animals evolve?
• Again kin-selection…
• All naked mole rats
Are close relatives b/c
Of inbreeding（近亲交配）.
• Ants/bees are haploidDiploid（二倍体循环）:
fertile eggs are
female, nonfertilized eggs
are male.
mate
Children
All female
Don’t
Mate =
Male
offspring
How did eusocial animals evolve?
• Again kin-selection…
• All naked mole rats
Are close relatives b/c
Of inbreeding.
• Ants are haploid-diploid:
Fertile eggs are female
Nonfertized eggs are male
What is r for mother
And daughter?
50%
How did eusocial animals evolve?
• Again kin-selection…
• All naked mole rats
Are close relatives b/c
Of inbreeding.
• Ants are haploid-diploid:
Fertile eggs are female
Nonfertized eggs are male
What is r for
Two sisters?
100 + 100 + 50 + 50 / 4 = 75%
Kin selection = an explanation for
altruism
.
W. D. Hamilton (1936-2006)
Haploidiploidy 
High relatedness among
female workers 
Eusociality?
One of most famous results of
Behavioral Ecology.
But doesn’t explain the termites
that are also eusocial but not
haplo-diploid.
Today’s lecture
•
•
•
•
4 questions of behavioral ecology
Nature vs. nurture
Foraging ecology
Charles Darwin’s two biggest problems:
– Sexual Selection
– Group Living and Altruism.
• Looking at human behavior
Kin selection in humans?
Who would you help out of a burning fire?
Tend to save related people
0.5
Save younger people who
Have more chance of reproducing
0.25 0.12 0.0
Relatedness
From Buss “Evolutionary Psychology” (2008)
Kin selection in humans?
A more subtle prediction:
Because human fertilization
internal, male paternity uncertain.
Hypothesis: Maternal grandparents
（外祖父母）should invest more
because they
are more sure of their genes
are represented.
Sexual selection in humans
• Men are less
choosy!
• Women investment
higher: 9 months +
lactation can last in
some cultures up to
4 years.
Likelihood
To have
Sex
Length know partner
Sometime to consider: could this be cultural
（文化的）rather than biological? … Could
young men be taught that being sexually
outgoing is appropriate, and women be taught
it’s not so?
Women’s options: long-term vs. short-term mating
strategies（策略）
• Advantages to marriage:
– Resources, care given by father increase chances
of success for children.
• Advantages to
short-term mating:
- good gene models?
- testing potential long-term partner?
It takes two to tango!
If men are opting for short-term
Mating options, women are too
Women’s presence for short-term mates:
good genes over caretaking?
Index of “Social
Dominance（优势）””
From Buss 2008,
After Gangestad et al. 2004
Women’s presence for short-term mates:
good genes over caretaking?
Symmetry（对称性）
Women prefer symmetrical
men particularly when they are fertile
and not looking for long-term partners.
From Little et al. 2007
Amazingly, women when they are fertile have been shown to
prefer the smell (sweaty T-shirt) of symmetrical men!
Gangestad and Thornhill 1998
Women’s presence for short-term mates:
testing long-term mates?
Care to dance?
Better dancers are more
symmetrical and
women are more
perceptive about men’s
dancing than men are
about women’s.
From Brown et al. 2005
Women’s presence for short-term mates:
testing long-term mates?
Care to dance?
From Brown et al. 2005
Homework
• Chapters 9 and 10 for Saturday.
• Read the “sweaty T-shirt” study (Gangestad
and Thornhill 1998). Is their work convincing
to you? What are the strengths（重点） of
the paper? What are its weaknesses（缺点）?
Be prepared to discuss.
Key concepts
• Animal behaviorists ask different
kinds of questions: about how a
behavior occurs, how it develops,
what its adaptive functions are,
and about its evolutionary
history.
• All behavior is a mix of genetic
instructions and learning; but
behaviors differ in the proportion
with which they are genetically
encoded.
• Foraging theory is an example
where researchers have tested
whether animals make decisions
that increase their energy intake
and decrease how much energy
they spend foraging.
• Sexual selection can explain
elaborate ornaments of one sex:
these ornaments determine the
animal’s reproductive success.
Why “choosy” individuals select
ornamented animals is more
complicated, but perhaps they
are selecting good genes for their
offspring.
• Animals are more likely to help
their relatives than other
individuals (“kin selection”).
Because kin share the helpers’
genes, the helper is ensuring that
more of its genes are found in the
next generation.