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Predation

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

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  1. Predation Psychology 3106

  2. 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

  3. Possible Strategies • Live in a group • Camouflage • Armour • Fight back • Don’t taste good!

  4. 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

  5. Questions, Questions, Questions….. • Two evolutionary questions can be asked • 1) How did distastefulness evolve? • 2) Why are distasteful prey so obvious about it?

  6. 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…..

  7. 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

  8. 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

  9. 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

  10. Gittleman and Harvey (1980) • Chicks fed two grain types • Colour did not matter on its own • Distastefulness and colour are the key

  11. 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

  12. 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’

  13. 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

  14. 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

  15. 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!

  16. 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

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