Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> One thing I haven't figured out is why poisonous prey animals (frogs, 
>> butterflies, etc) wind up being brightly colored.
> 
>   AFAIK the bright colors work as a warning signal. Predators learn to
> distinguish the poisonous prey by their color.
> 
>   It would make little sense to just have poison but otherwise look edible.
> Both predator and prey get killed. With a warning color both live.
> 
>   (By this logic it would follow that some species mimic the color of
> poisonous species. I wonder if there are examples of this.)
> 

Another way to look at it is that poisonous animals can be any color 
they want. They already have a defense system (the poison) and don't 
require a second one. Non-poisonous animals lack this defense system, so 
they need to be doubly careful. What they need is their own, *different* 
defense system (the blending in part) so *they* don't get eaten.

Also, as far as the color-as-warning-system goes, it's not like the prey 
animals decided one day that they wanted to be bright yellow or bright 
red. Rather, the predator animal needed help distinguishing poisonous 
animals from non-poisonous ones in order for *it* to survive. Predators 
who didn't learn to distinguish them died and failed to pass on their 
genes, resulting in future generations with a better ability to make the 
color distinctions. Since these future generations are better able to 
distinguish by color, a *second* result is that fewer bright-colored 
poisonous prey animals get eaten. Thus, there's a kind of feedback loop, 
and the behavior of the predator animal (the behavior of the prey animal 
is generally irrelevant) influences the evolution of the prey animal 
along two separate axes.

Finally, only animals that are poisonous *when eaten* (or maybe, low on 
the food chain) tend to be brightly-colored. Animals that use poison to 
*kill their prey* (or, high on the food chain) are not brightly-colored.

-Mike

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