Taken from: The World Book Encyclopedia
Copyright: World Book, Inc. 1995

Frog is a small, tailless animal with bulging eyes. Almost all frogs also have long back legs. The strong hind legs enable a frog to leap distances far greater than the length of its body. Frogs live on every continent except Antarctica. But tropical regions have the greatest number of species. Frogs are classified as amphibians. Most amphibians, including most frogs, spend part of their life as a water animal and part as a land animal.

Frogs are related to toads but differ from them in several ways.

The first frogs appeared on earth about 180 million years ago. About 3,800 species of frogs and toads have developed from these early ancestors. Some species spend their entire life in or near water. Others live mainly on land and come to the water only to mate. Still other species never enter the water, not even to mate. Many kinds are climbers that dwell in trees. Other are burrowers that live underground.

Throughout history, frogs have been the source of superstitions. One old myth says that frogs fall from the sky during a rain. Actually, many species that liver underground leave their burrows during or after a rain at the start of the mating season. Because people seldom see these frogs the rest of the year, they imagine the animals fell from the sky with the rain.

Frogs, like all other amphibians, are cold-blooded----that is, their body temperature tends to be the same as the temperature of the surrounding air or water. Frogs that live in regions with cold winters hibernate. Some species hibernate in burrows. Others spend the winter buried in mud at the bottom of a pond or stream, breathing through their skin. During hibernation, a frog lives off materials stored in its body tissues.

Frogs benefit us in many ways. They eat large numbers of insects, which might otherwise become serious pests. Frogs also provide us with food. The meaty hind legs of larger frogs are considered a delicacy in many countries. In the United States, people mainly eat the legs of bullfrogs, green frogs, and leopard frogs. Frogs also are used widely in the laboratory. Medical researchers use frogs to test new drugs, and students dissect frogs to learn about anatomy.

Human beings are, in fact, the frog's worst enemy. People obtain most of the frogs used for food and in the laboratory from the wild. Furthermore, people destroy the homes and breeding places of frogs by replacing natural areas with cities and farms. They also pollute and so poison the waters in which frogs dwell.