Download “Behavioral Adaptations for Survival”. Really about predator/prey

Alcock Chapter 6 - “Behavioral Adaptations for
Survival”.
Really about predator/prey relationships.
In the larger context, this is one aspect of
Behavioral Ecology
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There are different interactions between
organisms -predator-prey
parasite-host
symbiosis
mutualism
The interactions relative to predatory-prey
and parasite-host involve communication.
It is often interesting to analyze whether
the communication is honest or deceitful.
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Cryptosis & mimicry. These anti-predator
strategies may involve one or more forms of
biological deceit -- that is, you attempt to
portray yourself as something different from
reality.
Cryptosis involves:
•  hiding
•  mimicry
•  camouflage
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Leaf Mimicry
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Biston betularia
(camo moth)
Question:
What does the previous example (Figure 6.16
in the text) have to do with behavior?
Ans: It prevents eating behavior by the predator! (but also moths must choose appropriate background)
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DIFFERENT TYPES OF CAMOUFLAGE
Background matching (like the moths)
Countershading – common in fish and
birds
Edge Disruption
Form Disruption
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VENTRAL
COUNTERSHADING
EDGE DISRUPTION
Which image is
more readily
identified as a
snake?
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FORM DISRUPTION (DISRUPTIVE COLORATION)
Zebra salad
Vertical stripes = vertical grass
Predators often cue on
eyes (an attack releaser)
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Using an anti-predator behavior to discuss
the testing of hypotheses about behaviors…
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Skipper butterfly caterpillars eject feces from their
hiding spots....
A wasp preys on the caterpillars. Are the caterpillars
harder to find by the wasps if feces are not present?
Hypotheses: Fecal ejection (FE) removes a chemical
cue that helps the wasp find the caterpillar.
Set up experiment where caterpillar hiding spots fitted
with added feces or dummy feces.
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Set up experiment where caterpillar hiding spots fitted
with added feces or dummy feces.
?
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Results: Wasps do visit fecal nests more often and for longer
times.
The wasp’s interest:
Be careful of interpretation. Did we “prove” the
hypothesis?
The fact that the wasps prefer hiding places with
feces does not prove the caterpillar’s behavior is a
wasp anti-predator strategy that removes a chemical
cue.
Other possibilities:
1.  FE could have evolved for another reason, but
happens to also work against wasps.
2.  FE could have evolved to evade a different predator,
but happens to work against wasps too.
3.  Another trait could have been selected for, but FE is
linked to it.
4.  FE could be an anti-predator strategy that has
nothing to do with chemical cues. (Maybe FE is a
way to shoot down wasps…)
This beetle blasts away at ants!
A better approach is to try and disprove a hypothesis.
Hypothesis #2:
FE is for hygiene, not an anti-predator mechanism.
Testable!
Add or subtract feces and measure health (e.g. growth
rate of caterpillars.
Turns out there is no health benefit.
Reject hypothesis #2. Make strong statement that FE
is NOT for hygiene. (Eventually eliminate all
alternative hypotheses)
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MULTIPLE SELECTION PRESSURES – cryptosis
behavior vs advertisement…
There may be more than one selective force leading to
apparently maladaptive or conflicting behaviors.
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Tungara frog (Physalaemus pustulosus) gives a
variable advertisement call.
If multiple males heard (= more male competition for
females), frog produces a call more attractive to
females.
… but the more attractive
call makes the male frog
more vulnerable to
predation.
So males balance need to
attract females with need
to stay alive!
The bat Trachops can more easily localize the frog when
it gives the whine+chuck call, the call more attractive to
females.
Squirrels calibrate their anti-predator behavior
against snakes using a cost-benefit analysis.
The more threatening the snake, the less
aggressive is the squirrel!
Mobbing by rock squirrel
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PARASITE-HOST BEHAVIORAL
INTERACTIONS
Deception is also prevalent with parasitehost interactions. Consider the famous case
of Oropendolas and Cow birds...
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Oropendola
… and nest
Cowbird
Bot flies and a squirrel with an infestation.
Deceptive signal
I am not who I appear to be.
By being cryptic: You
didn’t really hear a
frog…
By appearing more fierce:
Are you sure I am not
dangerous to you?
Intimidation mimicry
The caterpillar Hemeroplanes ornata
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A deceptive mimic -- The fly mimics the very
predator that is after it.
fly
jumping spider
Honest (non-deceptive) signals also can used
as anti-predator devices:
Stotting in
Springboks/
Gazelles
Hypotheses for why stotting occurs:
1.  Alarm signal: Warn neighbors who are related to you.
2.  Social cohesion signal: Do it to bring group together.
3.  Confusion effect: Predator will be confused by odd
behavior and go after someone else in the group.
4.  Honest signal of unprofitability: Anyone who can jump
that high can outrun me, says the predator, I better pick
a different target.
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Predictions from each hypotheses
You honestly communicate to the predator that you are the
most costly prey item. Of course this strategy only works if you
are in a group, and the predator has the sophistication to get
the point!
So the behavior works…
… but is it confusion or unprofitability?
For stotting to work, first there had to be herding.
Why is there herding behavior? Or schooling behavior?
Many individuals moving in a coordinated way
become a large visual mass. That is, the predator
doesn’t see many fish, the predator sees a large
undulating “whale”.
Hypothetically, a gene shows up that causes one
individual to prefer hanging close to a con-specific. A
predator eats your neighbor, and you leave more
genes in the next generation. So the “grouping” gene
becomes fixed.
Everyone trying to hide behind everyone else
makes an instant herd.
As a corollary, the most aggressive and
strongest individuals should successfully
compete for the best position in the herd (the
center).
Individuals in large groups have lower predation risk
Anolis doing a push-up. Is this an honest signal of
unprofitabilty?
Again, must be careful about interpretation.
Do we know if snakes can make such a judgment?
Do we know if a lizard with more endurance has a
greater ability to avoid snakes?
Maybe push-ups are just the residue of excitement.
SOCIAL INSECTS AND GROUP DEFENSIVE BEHAVIOR
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Social learning of predators vs. innate fear
Monkeys have no innate fear of snakes, but if they
are shown a video of another monkey being afraid
of a snake, then they become afraid of snakes, too even if they have never seen a real snake before.
This is also true for spiders, but not for clowns.
(How would the amygdala learn to recognize a
clown? )
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Summary
So we see that in some cases there are structural aspects to
anti-predator strategies, and the use of these requires particular
behaviors. Sometimes these behaviors are minimal.
In other cases, there is just a behavior.
Anti-predator strategies include:
o  being cryptic
o  being confusing
o  being intimidating – typically with a deceitful signal
o  communicating poor value with an honest signal
o  being in a collective
o  the value of avoiding predation has to be balanced by the
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cost of not being available for feeding, reproduction,
etc.