True Frogs: Ranidae

Physical characteristics: The largest frog in North America, the bullfrog can grow to 8 inches (20.3 centimeters) and weigh more than
3.3 pounds (1.5 kilograms). It may be green, brown, or greenish brown, sometimes marked with dark spots on its back and legs. It has long, strong hind legs with toes that have full webs between them. It has a pair of large eardrums showing on each side of the head. Males and females look much alike, except the male's throat is yellowish and the female's is cream-colored, and the male's eardrum is much larger than the eye, while the female's is about the same size as the eye. The bullfrog looks similar to another species, known as the green frog (Rana clamitans). The green frog, however, is smaller and has a fold of skin running down each side of the back. The Many high school students are familiar with this species as the frog they dissect in biology class. It also has other uses. This frog is captured for food, and its legs are served at restaurants across the United States and elsewhere. (Hans Pfletschinger/Peter Arnold, Inc.) bullfrog does not have these long folds. Instead, it has a smaller fold that curls from the back of the eye around the eardrum.

Geographic range: The bullfrog is an eastern North American species that lives in northern Mexico, the United States, and southern Canada. Over the years, it has also been introduced to other places in the world, where it does very well including parts of Central and South America, the West Indies, several countries in Europe and southeastern Asia, and some ocean islands, including Hawaii.

Habitat: It makes its home in almost any large, calm body of water, including ponds, bays of the Great Lakes, slow backwaters of rivers and streams, and marshes that are filled with water all year long. Adults are not found in wetlands that dry up for part of the year. In Hawaii, some bullfrogs can even survive in somewhat salty water.

Diet: Bullfrogs hunt by ambush, which means that they sit still and wait for their meals to come to them. Meals may include other frogs, including bullfrog tadpoles and other, younger bullfrogs; various animals, such as snakes, fish, ducklings, and other birds; and many different kinds of invertebrates, like insects, worms, spiders, and snails.

Behavior and reproduction: It usually stays along the edge of its water body, sitting among reeds and other plants that are in the water or just on shore. This frog is active during warm weather. When the cold autumn temperatures arrive, it buries itself in the muck at the bottom of the water and enters hibernation until warm weather returns in the spring. During the breeding season, which runs from spring to mid-summer, each male will defend his piece of shoreline against other male bullfrogs by first making a short warning call, and if that does not work, by pushing the male frog, sometimes even getting into wrestling matches. Males make loud, deep calls, which some people describe as sounding like a slurred "jug-o-rum." A male and female pair may mate at the calling site or move a sort distance away. A female can lay three thousand to twenty thousand eggs, each of which measures only 0.05 to 0.07 inches (1.2 to 1.7 millimeters) across. The eggs hatch within a week into small tadpoles. Unlike the tadpoles of most other species, which turn into froglets within a few months, bullfrog tadpoles may wait from two to four years and grow to 6.7 inches (17 centimeters) long before making the change.

Bullfrogs and people: Many high school students are familiar with this species as the frog they dissect in biology class. It also has other uses. This frog is captured for food, and its legs are served at restaurants across the United States and elsewhere.

Conservation status: This is a very common frog and is not considered to be at risk. Instead, it has become a pest species in many areas of the world where humans have introduced it. This is because the bullfrog not only competes with other species for their food but also eats the other frogs. ∎