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Predation. Psychology 3106. Introduction. You hear quite a bit about foraging Foraging is a two way street There has to be a ‘foragee’ as well Just as foragers have evolved strategies, so have prey. Possible Strategies. Live in a group Camouflage Armour Fight back Don’t taste good!.

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predation

Predation

Psychology 3106

introduction
Introduction
  • You hear quite a bit about foraging
  • Foraging is a two way street
    • There has to be a ‘foragee’ as well
  • Just as foragers have evolved strategies, so have prey
possible strategies
Possible Strategies
  • Live in a group
  • Camouflage
  • Armour
  • Fight back
  • Don’t taste good!
aposematism
Aposematism
  • Some insects taste bad and are obvious about it
  • Usually have a diet of plants that does not taste good to the predator
  • The Monarch butterfly is great example
questions questions questions
Questions, Questions, Questions…..
  • Two evolutionary questions can be asked
    • 1) How did distastefulness evolve?
    • 2) Why are distasteful prey so obvious about it?
question 1
Question 1
  • Well, it should increase the probability of the prey surviving
  • But, the predator has to sample a prey item in order to learn that it will get sick
  • How does the fitness of the prey item increase if it has been eaten?
  • Species level?
    • Not a chance in hell…..
so how then
So How then?
  • Well, here’s a hint: Usually aposematic bugs are gregarious
  • Usually they are surrounded by siblings
  • If only a few of the brood are eaten then the frequency of the distasteful gene will spread
  • (Fisher, 1958) one of the first kin selection models
why be so obvious then
Why be so obvious then?
  • First off, not all distasteful prey are obvious
  • Most are though
  • Two possible explanations
    • Contrast with the background makes learning easier than learning about cryptic prey
    • Gibson (1974)
      • Blue, green or red millet on a green dot background
gibson 1974
Gibson (1974)
  • Feeding platform dropped when red ‘aposematic’ grain was eaten
  • The birds stopped eating red seeds, still ate the blue and green
  • Can’t be the background then, as the cryptic ones were still eaten
gittleman and harvey 1980
Gittleman and Harvey (1980)
  • Chicks fed two grain types
  • Colour did not matter on its own
  • Distastefulness and colour are the key
shettleworth 1972
Shettleworth (1972)
  • Chicks learned to avoid unpalatable water if it was a novel colour (other than what they were raised on)
  • Novelty is the key, not contrast
  • So, could be that the prey evolved a strategy of being different as possible
kin selection
Kin Selection
  • Aposematism must have evolved through kin selection
  • Aposematic butterflies are gregarious
  • Cryptic butterflies are not!
  • Aposematic live longer than cryptic
    • They could still ‘teach a lesson’
other characteristics
Other characteristics
  • They have smaller territories
  • They roost communally
  • They have delayed sexual maturity
  • So, because they live longer they can teach the lesson more easily
mimicry
Mimicry
  • Some insects are aposematic and successful, why not copy?
    • Batesian mimicry
  • Colouration is similar to toxic species, but the prey item is not toxic
mullerian mimicry
Mullerian Mimicry
  • In Mullerian mimicry, all species that share a colouration are dangerous
  • Many snakes use this
  • Also may have characteristics that make prey look like a predator!
conclusions
Conclusions
  • Evolution is basically an arms race
  • As fast as aposematism or crytic colouration evolve, species learn to detect the prey
    • Learn evolutionarily or in the real sense