Frog, a small tailless amphibian. Scientifically, there is no distinction between frogs and toads. Both belong to the same order of the class Amphibia, and are collectively called anurans. Popularly, anurans that live in or near freshwater are usually called frogs. They vary in size from certain South American frogs less than one-half inch (13 mm) long to the 10-inch (25-cm) goliath frog of Africa.

Most frogs are green or greenish brown, with various markings in darker or lighter color; some frogs, however, are brightly colored. The frogs of the United States and Canada are smooth-skinned, but in other parts of the world there are frogs with rough or irregular skins. Many kinds of frogs shed their entire skin periodically.

Frogs have webbed hind feet and most are fast swimmers.

Are All Frogs Green?

Not all frogs are green. Frogs can be green, gray, red, blue, yellow, purple, orange, or combinations of two or more colors. Whether their skin is plain or eye-catching, it serves as an adaptation: it helps them stay safe.

Some frogs use their skin as camouflage, to help them blend into their environment. Certain frogs even change their skin color with changes in humidity, light, and temperature.

Highly toxic frogs display bright colors to warn predators (PRED uh tuhrz) not to eat them. And some nontoxic frogs display bright colors so predators will think they’re poisonous, too.

Frogs shed the outer layer of their skin many times a year. So do toads. They use their forelegs to pull the old skin off over their heads. Then they eat it.

A frog can breathe not only with its mouth and lungs but also through its skin. In order to breathe through the skin, it must keep its skin moist. Some frogs stay near water; others have developed some adaptation to prevent drying out, such as burrowing into the soil or hiding under rocks. A frog's skin is permeable to water as well as air, and for this reason, a frog can easily absorb harmful chemicals from its environment. As wetlands are dried up by developers, populations of frogs are threatened with extinction.

What’s Under All That Thin, Wet Skin?

A frog is a vertebrate, or an animal with a backbone. Like other vertebrates, a frog also has organs, such as a heart, a liver, kidneys, and lungs.

But a frog is different from other vertebrates. A frog’s heart has three chambers, not four. Frogs can breathe through their skin as well as their lungs.

All frogs have the same basic body structure. They have short front legs and flat heads and bodies. After they grow out of the tadpole stage, frogs don’t have tails.

Most frogs have large back legs, which help them hop from place to place. But a few frogs that dig burrows have short hind legs. They can’t hop at all.

All frogs have short front legs and large, strong hind legs for jumping. The hind feet are webbed, and most frogs are fast swimmers. The flying frog of Asia has both front and hind feet webbed, and uses them to glid from trees to the ground. Tree-climbing frogs have suction pads on their toes. Frogs have well-developed senses of sight and hearing. The male of each species has a distinctive call, used in finding a mate. Frogs of many species secrete poisonous substances as a defense against predators.

Are All Frog Feet the Same?

Different kinds of frogs have different kinds of feet. Frogs that live in or near water have webbed toes on their hind feet. The webbing helps them swim quickly through the water. Flying frogs, which glide from tree to tree, have extra webbing on their front and hind feet. This extra webbing helps the frogs glide through the air.

Some tree frogs have no webbing at all on their feet. Instead, these frogs have sticky pads on the ends of their toes. The pads help them cling to the surface of tree trunks, twigs, and leaves as they climb.How Far Can Frogs Jump?Some frogs can make impressive jumps. Many frogs can leap 20 times their own body length. Some tree frogs can jump over 7 feet (2 meters). That’s nearly 50 times their body length. That is like a 6-foot (1.8-meter) human jumping 300 feet (90 meters).

Not all frogs are great jumpers, however. Some frogs that dig burrows, for example, have short hind legs. Many of them hop weakly, if at all.

Frogs are found in the temperate and tropical regions of all continents. They cannot live in extremely cold climates or at high altitudes.

Where in the World Do Frogs and Other Amphibians Live?

Frogs have lived on Earth for about 180 million years, and they’ve developed ways to live on every continent of the world except Antarctica. Today, most frogs live in tropical regions.

Different kinds of frogs live in different habitats. Members of the common group of frogs, known as “true frogs,” usually live in or near water. They have long hind legs, smooth skin, and webbed hind feet.

Tiny tree frogs dwell in—you guessed it—trees. Other frogs live on rocky cliffs, or in swift mountain streams. Some kinds of frogs live in burrows and eat ants and termites.

Many kinds of frogs and other amphibians live their whole lives in or near water. But some leave the water when they become adults and only return to mate and lay eggs or bear their young. A few types of frogs never enter the water.

Why Are Frogs So Cold?

Like all amphibians, frogs are ectotherms (EHK tuh thuhrmz). They can’t warm themselves up or cool themselves off. They have to rely on their habitat to do that for them.

People say frogs are cold-blooded animals, but their blood isn’t really cold. Their body temperature tends to be the same as the temperature of the surrounding air or water.

When the weather gets too hot and dry, frogs often estivate (EHS tih vayt), or sleep underground away from the heat. When they sense moisture in the soil, they awaken and come to the surface.

Frogs that live in areas that have winter hibernate (HI buhr nayt) to escape the cold. They may burrow under leaves or mud at the bottom of a pond or stream. Or they may dig down as much as a foot underground, often under rocks or rotten logs.

The hind legs of any species of frogs are prized as food. Indians in Colombia obtain poison from the skin of certain species of poison-dart, or poison-arrow, frogs and apply it to blowgun darts they use in hunting.

Are Some Frogs Poisonous?

Most frogs are harmless, but some frogs, as well as some toads, have glands that ooze poison onto their skin. The poison dart frogs of Central and South America make a poison on their skin strong enough to kill almost any predator. Indians in this region have painted this poison on arrows to make them deadly.

Most of the other kinds of poisonous frogs emit only a mild poison. Some of these frogs simply taste so bad because of the poison that no one wants to eat them. But others are deadly to small predators. Often, the brighter the frog is, the more deadly the poison it emits.

Mildly poisonous frogs are usually harmless to humans, but even mild poisons can irritate your eyes. Be sure to wash your hands after handling a frog. Also, keep frogs and toads away from pets. Poison that may only irritate a human could have a worse effect on a smaller animal.