ORDER

Anura (frogs and toads)

FAMILY

Ranidae (riparian frogs and true frogs)

HABITAT AND RANGE

North American bullfrogs are only native to the near arctic region. They are found from Nova Scotia to central Florida, from the East coast to Wisconsin, and across the Great Plains to the Rockies. The natural western limits of this species are now confused due to their introduction into places as far west as California and Mexico. North American bullfrogs must live in water and are therefore usually found near some source of water, such as a lake, pond, river, or bog. Warm, still, shallow waters are preferred.

IDENTIFICATION

North American bullfrogs are the largest true frog found in North America, weighing up to 0.5 kg and 203 mm in length. Color varies from brownish to shades of green, often with spots or blotches of a darker color about the back. The sex of an adult bullfrog can be easily determined by examining the size of the tympanum (the external ear of the frog) relative to that of the eye. The tympanum is a round circle located on the side of the head near the eye, and in males it is much larger than the eye. In females the tympanum is as large as or smaller than the eye. Also, during the breeding season the throat of the male bullfrog is yellow, whereas the female's is white.

DIET

Bullfrogs are predators. They usually eat snakes, worms, crustaceans, frogs, tadpoles, and aquatic eggs of fish, frogs, insects, or salamanders. They are cannibalistic and will not hesitate to eat their own kind. Bullfrog tadpoles mostly graze on aquatic plants.

REPRODUCTION AND LIFESPAN

Breeding takes place in May to July in the north, and from February to October in the south. Fertilization is external, with the females depositing as many as 20,000 eggs in a foamy film in quiet, protected waters. Fertilization is usually, but not always, by one male. Tadpoles emerge about four days after fertilization. These tadpoles may remain in the tadpole stage for almost 3 years before transforming into frogs. Adults reach sexual maturity after 3 to 5 years. Lifespan in the wild is about 9 years, the record for captivity, however, is 16 years.

NOTES

North American bullfrogs prefer warm weather and will hibernate during cold weather. A bullfrog may bury itself in mud and construct a small cave-like structure for the winter.