Friday, June 1, 2007

Warning Colors

I thought I understood well how warning colors function in nature. It makes perfect sense to me that a blue jay – new to the world – would sample a monarch butterfly. And that after vomiting and feeling quite terrible, he would choose not to eat any more of those orange and black-striped critters. I understand that the blue jay’s experience didn’t help the individual monarch whom he ate, but does benefit the monarch’s relatives within the jay’s territory.

It is also easy to see how a bobcat might approach a skunk, have a negative experience, and learn from it. In fact, I can find innumerable examples of how warningly colored animals teach predators a lesson they will not likely forget.

But what about that coral snake? One can’t learn every lesson first-hand. If a coyote tries to eat a coral snake, it may not survive the experience. Who would that be a lesson to? No one. Unless you want to try to convince me that the coyote had an audience, and that the onlooker learned to avoid coral snakes vicariously.

In The Birder’s Bug Book, Waldbauer speculates that it is possible that the coral snake actually mimics some other, less venomous snake. He supposes that the coyote encounters the other red, yellow, and black snake, and is assaulted with some mild venom. By the time he sees a coral snake, he knows to avoid the aposematic colors.

That’s a thought.

But what is that other snake? This snake would have to be nearly every place the coral snake is…from North Carolina to Argentina. There are 52 kinds of snakes in Louisiana. There are 5 venomous snakes besides the coral snake: pygmy rattlesnake, copperhead, cottonmouth, timber rattlesnake, and eastern diamond-backed rattlesnake. None of these contestants could win a coral snake look-alike contest.

So here’s what I think: Snake-eaters don’t learn to avoid red, black, and yellow rings. They are born with the instinct to avoid those colors. Add this behavior to hundreds of others that we already accept as instinctual (from how sea turtles get back to the same beaches where they started their lives to lay their eggs, to how my dog always makes three circles before lying down), and doesn’t it just make sense?