HerpIndiana

American Bullfrog (Lithobates (Rana) catesbeianus)

Description

Coloration: A large, green or brown frog with no dorsolateral ridge. Dorsal coloration varies from dark mottling to uniform green. Ventral coloration is light with gray mottling. The throat of males is often covered with a yellow wash. The tympanum of males is quite large, while that of females is closer to eye-size. Bullfrogs are most likely to be confused with Green Frogs, but the latter has obvious dorsolateral folds (Minton 130-131.

Size: Large adults of this species can grow to lengths of 6-8 inches, though most adults are around 4 or 5 inches (Minton 131).

Larvae: Tadpoles are very similar to those of the Green Frog. Bullfrog tadpoles grow larger (around 4 inches) and have finer mottling on the tail fins, often restricted to the dorsal fin (Minton 132).

Eggs: Eggs are laid in a film on the surface, and as many as 10,000 eggs are laid in a mass (Minton 133).

Distribution

American Bullfrogs are found throughout the state (Minton 132).

Activity

Bullfrogs are active from early or mid-spring to mid-fall.

Breeding Season: Bullfrogs breed in Indiana from late May to early August (Minton 133).

Taxonomy

Bullfrogs are members of the genus Rana, which consists of 7 other species in Indiana, and are in the family Ranidae.

Natural History

Habitat: Bullfrogs inhabit a wide array of aquatic situations, though permanent water is necessary. They prefer slow water, from swamps to slow rivers (Minton 132). I have often observed them sitting on the shoreline of ponds and slow portions of rivers. When approached, Bullfrogs will dive into the water and disappear, often under leaf litter. Though large bodies of slow water seem to be the preferred habitat, I have seen many Bullfrogs (mostly young in age) in small, rocky streams, where they are flipped under rocks with Green Frogs.

Feeding: Bullfrogs are voracious predators and will eat just about anything. Insects and crayfish are large parts of the diet, though vertebrates like other frogs, tadpoles, small turtles and snakes, and small mammals are also reported (Minton 134).

Breeding: Bullfrogs breed from May to August in slow, shallow water. They generally breed in permanent water because their tadpoles often take more than one year to develop (Minton 132). However, I have observed Bullfrogs breeding in ponds that dry up in the late summer and fall.

Call: Bullfrogs have a deep, resonating call, which is often repeated in several minute intervals (Minton 133). I have heard its call oberserved by many as "jug-o-rum."