Eating Habits of Reptiles (Part 11)

It may never be possible to prove satisfactorily that a rattlesnake evolved its rattle as a safety device, but common sense certainly supports this conclusion. Such mechanisms, however, if they actually work, as they seem to, work in a complicated way. They must depend for their effect on a reactive mechanism in the potential enemy—that is to say, a concurrent evolutionary change that might produce in deer, for example, a tendency to shun prettily banded snakes or in coyotes to jump away from the buzz of a rattlesnake’s rattle. This is not hard to imagine, however. There are abundant cases in nature in which two different kinds of animals go through concomitant evolutionary changes that fit them for beneficial contacts with each other or reduce friction between them. In the relationships among living things harmony is at least as important as strife as a means of survival. A crab may cause havoc among the small animals that are its food, but at the same time it tolerantly goes about with a sea anemone on its back, or even makes overt moves to put the anemone there. The stinging cells of the anemone are protection for the crab, and its partner eats the scraps from the crab’s feeding.

Though at first glance it may seem silly to use such an example to illustrate relationships between poisonous snakes and other animals, it is not silly at all. Both the rattlesnake and a bison, say, are potentially dangerous to each other. Neither can get the slightest good out of contact with the other. On the other hand, both can profit immensely by staying completely out of one another’s way. What, then, is more logical than the snake should evolve a warning device, and the potential enemy—the inadvertent trampler—the psychology to react to the warning? Even a carnivore that usually ate snakes—unless it was immune to snake venom—would logically be better off if it had a heritable ability to recognize, or to learn to recognize, harmful snakes. Then it could go about its business of eating harmless snakes without any trouble. The striped coloration of coral snakes would surely entrench any such discriminatory capacity as might be found naturally in a hawk or any other snake-eating predator. So would the rattlesnake’s hair-raising warning.

To be continued…

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