Alice Calvert, of Portland, Maine for her question:
Why are leopards spotted and zebras striped?
Every year, millions of little beasties are devoured by larger beasties Every year, the frog population is cut down by hungry snakes, birds, weasels and foxes. But there are always enough frogs left to start next year's crop of tadpoles, If one year all the frogs escaped, the world would be plagued with frogs. They would soon perish from hunger.
Nature plans to save so many, but not too many, of each creature. This eating and being eaten plays a part in the balance of Nature. Countless tricks are used to keep so many, but not too many, creatures alive.
One trick is to dress each creature to match its background. This works two ways. It hides a little creature from his enemies. It makes it easier for a larger creature to sneak up on his victims. For everyone knows that a green coat is hard to spot in a leafy forest. But it shows up on a sandy beach.
Tigers, zebras and leopards look very conspicuous when you see them in their cages at the zoo. But each one wears a coat that blends in with his native background, The grass eating zebra is most interested in hiding from his catty enemies. Tigers and leopards are fearless meat‑eaters most interested in sneaking up on their victims.
The frisky zebra is a native of the brush country and the grassy belt lands of Africa. He walks on hoofs and cannot climb trees. At distance, the ground around him looks striped with slender shadows of dark and light. If he stays still, the zebra is not noticeable in the daylight or in the bright moonlight.
The tiger can climb. But he prefers to stalk along the bungle floor. He is a native of Asia where the bungle grasses are tall and often dried yellow. In bright sunlight they east almost black shadows. So the tiger is the least noticeable in a coat of black and yellow stripes. Such a coat makes him almost invisible until too late for his victim.
He is feared wherever he roams, for he kills without mercy. The handsome leopard loves to climb trees. He loves to spend his afternoons loafing in the branches, here the leaves cast mottled shadows of light and dark. The leopard's yellow coat is dotted with round rosettes of dark spots. Such a coat blends very well with the dappled sunlight and shadow. He dozes or waits to pounce on a forest deer walking below.
Moat animals seem to sense that their coats help to hide them against their backgrounds. The hunted tend to remain perfectly still when trouble threatens, The hunters crouch and creep up stealthily upon their prey. A speckled woodcock will freeze perfectly still on her nest among the speckled leaves when she senses trouble. A white polar bear will inch along bit by bit as he sneaks up on a fat seal. Little animals with this kind of sense are most likely to stay alive. Hunting animals with this kind of sense are not' likely to perish from hunger,