How does an animal avoid being eaten? by 6TpAe1Pr

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									How does an animal avoid being eaten?




                                        1
5/27/08: Behavioral adaptations for survival

               Lecture objectives:

               1. Be able to generate hypotheses
                  and predictions
                  for the adaptive value of a
                  potential antipredator strategy

               2. Recognize the antipredator
                  benefits that might arise
                  from living in groups


                                                    2
Detection   Attack   Capture




                               3
Minimize risk of detection
1.




      Must consider
     benefits and costs




                             4
Minimize risk of detection

2.




                             5
  Minimize risk of detection

  2. Crypsis
  (morphology & behavior)


                                         African assassin bug


Hypothesis: Assassin bug “backpacking”
is an adaptive antipredator behavior




                 Predictions?



                                                                6
  Minimize risk of detection

  2. Crypsis
  (morphology & behavior)




Hypothesis: Catocala relicta (moth) perching
behavior is an adaptive antipredator behavior

Predictions:
1. moth background choice:
2. bird predation:

                                                7
 Minimize risk of attack
 1.




  Hypothesis: Anolis lizard push-ups
  are honest signal of health


                           Predictions?

**Human female self-defense strategies**
“Crime victims are frequently chosen because they are easy targets. Criminals prey on
the weak or unsuspecting and usually avoid people who are aware of what’s going on
and might put up a fight. When out in public, look people in the eye, keep your head
up and walk with confidence.” -Realistic Female Self Defense Company                    8
Minimize risk of attack
2.


                                             Stinging insects
Individuals or groups?




                                              Sawfly larvae
                                          (with eucalyptus oils)
     Mobbing behavior: finches vs. hawk
                                                                   9
Minimize risk of attack
3.




                                              Skunks




     Poison dart frog     Monarch butterfly

                                                       10
Minimize risk of attack                       a)


4.

                                                   Model   (acoustical) Mimic:
Mimic:                                                       burrowing owl
a) an aposematic species (Batesian mimicry)
b) a predator of your predator
c) your predator




      b) Amazon caterpillar & Mexican vine snake
                                                                          11
 Minimize risk of attack
                                                              c) Tephritid fly and
                                                                jumping spider
 4. Deceive predator (mimicry)

Mimic:
a) an aposematic species (Batesian mimicry)
b) a predator of your predator
c) your predator

Hypothesis: Tephritid fly wing-waving
is an adaptive antipredator behavior

                           Tephritid fly      Tephritid fly             House fly

Predictions


                                                                                     12
Minimize risk of (lethal) capture
1.

Why might an ability to vastly outrun
a predator be unlikely to evolve?




                                        Flight muscle ratio   13
 Minimize risk of (lethal) capture
 2.




                 Desert gecko                        hairstreak butterfly

Hypothesis: Butterfly false heads help prey
            survive capture
                                       % escaping    30%
                                                                  10%
                                                    control    False head
                                                                            14
Minimize risk of (lethal) capture
3.




        Adelie penguins vs. leopard seal




                                           15
Minimize risk of (lethal) capture
3. Aggregate to reduce probability of capture
(dilution effect)


Is there safety in numbers?
The effect of cattle herding on biting risk from tsetse flies.




                                                                 16
Minimize risk of (lethal) capture
4.


     A group of individuals whose members use others as
     living shields against predators


        Position of nest       Snails/nest       Chases/fish/hr.

     Center of colony

     Edge of colony

     Away from colony



                                                                   17
Minimize risk of (lethal) capture
5.




                         Mean reaction
                          distance (m)

                           40


                           20

                            0
                                  1      2-10   11-50   >50
                                                              18
           Why do gazelles exhibit stotting behavior?
H1. Alarm signal: Warns conspecifics that predator is near.

H2. Confusion effect: Stotting individuals in a fleeing herd might
confuse/distract a predator so that it can’t focus on one prey
H3. Pursuit deterrence: Stotting advertises that the individual
is in good health and is unlikely to be captured




         Prediction             Alarm signal        Confusion        Deter pursuit

Stot when alone
Stot when in groups
Show rump to predator
Show rump to gazelles
                                                                                 19

								
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