True Frogs: Ranidae

Physical characteristics: The brown frog is sometimes called the European common frog or the grass frog. It is typically a tan frog, but some are darker brown, brownish green, gray, or black, and a few are tinted with red or yellow. Warts are scattered on its back, and these usually sit in small, dark brown blotches. The frog also has dark brown bands on its hind legs. Similar bands on its front legs are usually broken and fainter. It has a light-colored thin fold of skin down each side of its back and a dark patch of color behind each eye. Its head narrows toward the front to a somewhat pointy snout. The front feet are unwebbed, but the hind toes have a good deal of webbing between them. The underside of the frog is usually off-white or yellowish white in males and yellowish white to orange in females. During the mating season, the male's throat becomes blue-colored. Although this frog is found in much of Europe and is fairly common, scientists still are unsure what it eats. (© Stephen Dalton/Photo Researchers, Inc.) Adults grow to 2.4 to 3.7 inches (6.0 to 9.5 centimeters) long from snout to rump.

Geographic range: It lives throughout Europe.

Habitat: Adults mainly live along the forest floor or in grasses for most of the year. In the north where temperatures are cooler, they stay in lowland areas, but they may live high in mountains in the south, as much as 6,562 feet (2,000 meters) above sea level. The tadpoles develop in wetland areas.

Diet: Although this frog is found in much of Europe and is fairly common, scientists still are unsure what it eats.

Behavior and reproduction: In daytime it stays out of sight in damp areas. It becomes more active at night, when it does much of its hunting. It may also become active on rainy days. In northern climates where the weather turns cold in the winter, the brown frog hibernates at the bottom of a pond or under piles of rotting leaves and plants. As soon as the spring sun has melted the snow and ice from the ground and the frogs awaken, the breeding season begins. Males gather at the water and start calling, sometimes wrestling with one another over the females. To mate, a male climbs on the back of a female. The pair may remain together in this piggyback position for a few days. Each female lays one thousand to four thousand small eggs in shallow water. In about two weeks, the eggs hatch into tadpoles, which grow to as much as 1.77 inches (4.5 centimeters) long before they turn into froglets.

Brown frogs and people: They are common in country gardens and other places near humans. Some people in Europe eat these frogs.

Conservation status: Even though this frog is not considered at risk, some populations of it have become small because of over-collecting for various purposes, such as their use as food or their sale in the pet trade. Ecologists are also concerned about the effects of pollution on the frogs and about the draining of their breeding areas. ∎