Window on Nature
By Lowell & Kaye Christie, F47246
By and large, humans dress for the occasion — a swimsuit at the beach, boots for hiking, a nice dress or suit for weddings. But the picture is far more complicated and interesting in nature. A plant’s or animal’s appearance is primarily designed for survival — both individually and as a species.
One way this is achieved is through protective coloration. In general, this refers to the color or pattern that provides the wearer with protection from observation, either by predators or prey. In other words, it is its camouflage. Examples of such protection being used appear everywhere in nature.
A ground squirrel, in danger of being spotted by a coyote, must choose whether to freeze or to flee. The second option seems risky, because the coyote can run much faster than the ground squirrel. So, the squirrel opts to use its protective coloration. It crouches and stays motionless, allowing its drab colors and varied color pattern to blend right into its surroundings. These factors increase the squirrel’s life expectancy and, in this case, the coyote passes by unknowingly. But if their roles were reversed, the coyote might be the one to freeze, becoming nearly invisible even as its sharp eyes and active nose continue to search out its next meal.
Human hunters have the ability to take protective coloration a bit further. Dressing in a camouflage outfit allows them to blend into the background as they creep slowly and softly through the bush. Or they can simply crouch down, becoming invisible, while they wait for game to come by. In this case, both predator and prey used protective coloration. Quite often in nature, predator and prey are equally well concealed. It may be chance as to whether the unwary prey walks right into the coyote’s furry paws, or whether, by sitting tight, the squirrel lives to eat another day.
On another day, a bobcat crouches with its belly low enough to touch the ground, slowly stalking a squirrel through the grass. The bobcat can sense the squirrel is close, but can’t find it. Only a few feet away, the squirrel strains its eyes, searching the grasses for predators.
Rather than slinking through the brush unnoticed, some creatures flaunt their presence. Consider, for example, the flamboyant monarch butterfly.
Monarch butterflies are picky eaters when in the larval stage — very picky eaters. They settle for nothing but milkweed leaves. Nearly all species of milkweed are poisonous, so while eating the milkweed, the monarchs store up the poisons and become poisonous themselves. Thus, monarch butterflies don’t need to hide from potential predators. In fact, they show off their orange and black finery as though boasting, “Go ahead, eat me, buddy, and you’ll have the worst bellyache of your life!” When a predator (in this case, a bird) tastes a fresh monarch, it gags and wretches and determines that it won’t ever eat another one. So memorable is this experience that the bird won’t eat a butterfly that even looks like a monarch. This works to the benefit of all monarchs, and also to the look-alike viceroy butterfly. Viceroys aren’t poisonous, but since they often live in the same area as monarchs, viceroys get a free ride. After all, what reasonably intelligent bird is going to eat a butterfly that even resembles a monarch?
Viceroy butterflies are a good example of “mimicry” — copying, or mimicking, the appearance of another species. Mimicry also occurs in the reptile family, where several harmless snakes resemble their poisonous cousins. Perhaps you’ve seen how much a gopher snake looks like several desert species of rattlesnakes. The main difference between the snakes is that the bite of a gopher snake is painful, but it isn’t poisonous. But the gopher snake takes the mimicry a step beyond simply looking like a rattler. It mimics a rattlesnake by vibrating its “tail section” in an area with dry leaves. Take it from us; the experience of hearing that imitation rattle is as startling as hearing the real thing.
The plant kingdom also engages in mimicry. We hadn’t run across stinging nettles until we traveled into an area with an abundance of these ornery plants. Experiencing the stings from the tiny hairs of these plants was sufficient reason for us to avoid them. We’ve since learned that several harmless species of nettles resemble the stinging ones. Knowing that, we just may have to try out a recipe I found for steaming the young shoots and tender top leaves of nettles and serving them as greens — that is, if we can agree on who touches the nettles first to find out whether they are friendly or not.