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Mother Nature can play some tricks

  • A gray tree frog, which is native to Houston, is seen at the Houston Zoo on Friday, Feb. 8, 2008. (AP Photo/Houston Chronicle, Julio Cortez) Julio Cortez—AP

  • A gray tree frog pokes his head out from a bird house. The gray tree frog can adjust color to blend with trees. AP file



For the Monitor
Thursday, April 05, 2018

April Fool’s Day is a perfect time to explore some of the various ways that animals can fool us. They may change color, blend in with their surroundings or imitate something scary, distasteful or uneatable, all as a way to protect themselves.

Local mammals that change color with the seasons include the snowshoe hare and short-tailed and long-tailed weasels. In the warmer months their fur is brown to blend in with the leaf-covered forest floor. But in the fall, as daylight diminishes, they begin to transform into a completely white animal (except the tip of the weasels’ tail).

When winter snows arrive they are able to melt into the white surroundings. The pattern reverses at this time of year, when the insulating white fur is replaced by a brown pelt. Predators such as owls or foxes must use other senses besides sight to find these masters of disappearance.

Color change can also be triggered by location as is the case with the gray tree frog. In the gray phase, it is nearly invisible when clinging to the trunk of a maple tree. But if it moves to a tree with darker bark or to a white birch tree, it can change to nearly black or white to match its setting. Temperature and humidity may also cause a color change, but the end result is still a “now you see it, now you don’t” experience.

The invertebrate world provides many examples of color changes. The goldenrod crab spider appears yellow when it is skulking about on goldenrod flowers, hoping to snag a bug for dinner. But if it moves to a white daisy, it will turn white over the course of several days and blend it with its new home. This adaptation helps it sneak up on prey without being detected, as well as helping it avoid becoming lunch for a bird.

Cryptic coloration can be found in every animal phyla. Brown creepers are a favorite bird example. These small brown and white birds have both coloration and a flattened shape that help them match the pattern of tree bark as they skitter down the trunk, freeze in place and disappear.

Have you ever tried to find a wood turtle on the bottom of a flowing stream? Their sculpted shell looks just like a rock on the stream bed. Even if its head and feet are out, the orange blotches on the side of its neck and legs look like patches of sunlight filtered through the water. They nearly always win at hide and seek!

Camouflage is not always about hiding, it may also be exhibited as a disguise. We can be misled into thinking an animal is something other than what it is. If you dip a net into a stream or pond, you may bring up little clusters of sand stuck together or a tiny tube made of twigs or grass. Look closely. Inside these cases you might find a caddisfly larva. Each species of caddisfly is adapted to make a shelter out of the materials from the stream or pond bottom so that it will match its surroundings, not appearing to be an animal at all. A more familiar insect disguise is that of the walking stick. You may have seen one without ever knowing it, thinking you were looking at a delicate twig on a branch.

The larvae of the swallowtail butterfly don’t have to construct their costume. In the early instars of development they resemble bird droppings. That seems like an ideal way to keep from being eaten! Another method of deception is mimicry. The orange and black viceroy butterfly looks very similar to the monarch butterfly only smaller. The monarch contains a toxin that renders it distasteful to a predator, but the viceroy does not. Birds learn to avoid orange and black butterflies so the viceroy benefits from looking like something that tastes bad.

Examples of trickery abound in the natural world. It takes a careful and curious observer to determine what is there, what you are really looking at or if you are truly being bamboozled. But if you take the time to look you will be rewarded with nature’s surprises, and that’s no foolin’.