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Lecture

BIOL 208 (March 7, 2014) - Prey Defence, Ecology of Fear, Camouflage

4 Pages
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Department
Biology (Biological Sciences)
Course Code
BIOL208
Professor
James Cahill

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BIOL 208 (March 7, 2014) • *Defence may be constitutive or induced o *Constitutuve ex  cactus spines  *ALWAYS present (benefit of defence as a cost to opportunity) o Induced defence is defence only in the presence of danger  *If there is no risk, the maintenance cost dedicated to defence can be allocated elsewhere • Plant communication o When a predator is around o *Common o Ex. Between tobacco plants and between tobacco plants and other species. • Ecology of Fear o *Consumptive vs non-consumptive effects of predation  *Consumptive effects of predation = eating of prey o *A type of non-consumptive effect of predation is:  *The trade-off between foraging and risk of predation o *Death is actually rare… most prey don’t get eaten o Ex. sea cows  Graze on poor-quality seaweed beds in the presence of predators  Graze on high-quality seaweed beds in the absence of predators  *This is an example of non-consumptive effects of predation o *It is likely non-consumptive effects of predation that drive population dynamics.  *Ex. Rabbits in presence of predators = higher levels of stress hormones = decrease appetite = lower birth rates • Camouflage o Camouflaged in relation to the visual capabilities of the predator  Just because we can see them doesn’t mean that the predators will see them. • *Aposematic Colouration o *Poisonous bugs tend to be brightly coloured (full of nasty chemicals)  *Some harmless species take on this colouration to ward off predators. (Called batesian mimicry) • Predators conditioned to associate bright colours with poison/bitter compounds in the prey. • *Ratio of models/mimics is important for this system to work • *This type of mimicry can be seen as parasitism  *Can be seen as a type of refugia • Mullerian mimicry o *Species are of similar appearance BUT both/all of them are toxic • Ex. Wasps look like bees
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