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Desert Diary
Biology/Aposematic Coloration rule


Nature is full of warning signs: the bristling quills of a porcupine, a rattlesnake's buzz, the snarl of a cornered coyote. All say "Back off!", and when animals share the same warning sign, they have a distinct advantage. A predator that learns the warning takes heed regardless of its source.

Sharing is common among animals that depend on warning coloration. Conspicuous colors, especially patterns of black and white, black and red, or black and yellow, have one thing in common: they visually shout "danger!" But among animals, as with most people, there are always those who have to learn the hard way. For example, it usually takes several encounters with hornets and skunks to learn that a black and white pattern is shorthand for unpleasant and painful. By sharing a pattern, the damage received by any one species during the learning process is alleviated. A predator that requires five unfortunate encounters to learn avoidance often has killed or injured five individuals while learning—by spreading these damages among several species, no one population is badly depleted.
pen and ink


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.

Velvet Ant

A velvet ant—the red color says "Danger—Back off!" Photograph by A.H. Harris.



Web Resources

Aposematic Light. Young fireflies warn off predators with light.

Defensive Adaptations.

Wayne's Word. Great photographs of aposematically-colored poison dart frogs.