Taxonomy of organism
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Amphibia
Order: Anura
Family: Ranidae
Genus: Rana
Species: catesbeiana
Common Name: North American Bullfrog
bullfrog.jpg
Identifying characters
The largest true frog found in North America, weighing up to 0.5 kg and 203 mm in length. Typical length ranges from 90 to 152 mm. Color varies from brownish to shades of green, often with spots or blotches of a darker color about the back. The hind feet are fully webbed. 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. Also, during the breeding season the throat of the male bullfrog is yellow, whereas the female's is white.

Life cycle
Matting 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.
Ecosystem relationships (Habitat, Trophic level, Limiting factor(s), Competitors, Predators)
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. Bullfrogs are becoming increasingly common in areas that have been modified by humans. Increased water temperatures and increased aquatic vegetation, which are common factors of lakes polluted by humans, favor bullfrogs by providing suitable habitats for growth, reproduction, and escape from predators.\
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. Their hunting style is 'sit and wait.
Bullfrogs are predators. They usually eat worms, insects, crustaceans, frogs, tadpoles, and aquatic eggs of fish, frogs, insects, or salamanders. They are cannibalistic and will not hesitate to eat another bullfrog. Bullfrog tadpoles mostly graze on aquatic plants.
Humans hunt bullfrogs for frog legs, but they have a limited hunting season in most states. Bullfrogs are also eaten by a wide variety of other animals, depending on the region. These include herons, such as great blue herons and great egrets, turtles, water snakes, and raccoons. Most fish are averse to eating bullfrog tadpoles because of their undesirable taste.
Adaptations
During the winter months they hibernate and go into a state of energy conservation, which allows them to stay alive but not have to eat.

Bruening, S. 2002. "Rana catesbeiana" (On-line), Animal Diversity Web. Accessed July 11, 2011 http://animaldiversity.ummz.umich.edu/site/accounts/information/Rana_catesbeiana.html.