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Biological warfare and the coevolutionary arms race :

Pretty but deadly

To investigate the mystery of the hunters' deaths, Butch began by studying the newts. Rough-skinned newts, like the one found in the coffee pot, live along the west coast of the United States. The newts' brown backs blend into their surroundings; but when disturbed, the newts do something strange: they curl their heads and tails towards each other to show off their bright orange bellies. Why? Well, other brightly colored animals like monarch butterflies and coral snakes are poisonous or venomous. Their bright colors warn predators, "Back off, I'm dangerous!" Perhaps, Butch reasoned, the orange belly of the rough-skinned newt sends a similar message — perhaps the newts are poisonous.

rough-skinned newt rough-skinned newt displaying orange underside
Rough-skinned newts usually blend into their surroundings, but when disturbed they curl up to reveal a bright orange underside.
What's the difference between a poison and a venom? Need a hint? Monarch butterflies are poisonous and coral snakes are venomous — and either could make you pretty sick. If the toxin is actively injected, as by a snake bite or a bee sting, it is called a venom. But if the toxin is absorbed through the skin, inhaled, or eaten (as by the monarch's predators), it is called a poison.

monarch butterfly coral snake
Monarch butterflies (left) and coral snakes (right) are other toxic, brightly colored animals.

Newt photos provided by Edmund D. Brodie, III and Edmund D. Brodie, Jr.; monarch butterfly photo by T. W. Davies © California Academy of Sciences; coral snake photo provided by Paul M. Hampton

Biological warfare
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Dig deeper: find out more about organisms that warn their predators away in Aposematic Animals.