Lithobates catesbeianus

Bullfrogs are green or brown, usually with dark spots or mottling (but not large rounded spots). The eardrums are large, with a fold of skin curving around the top and rear edges. The hind toes are more or less fully webbed but the 4th toe extends beyond the webbing. There are no ridges along each side of the back. Maximum snout-vent length is about 8 inches (20 cm). In mature males, the eardrum usually is distinctly larger than the eye (same diameter in female and young), the throat is yellow during the breeding season, and the base of the thumb is swollen. Expansion of the internal vocal sac in adult males causes a bulging of the throat. The breeding call is a deep bellowing um-rum or um-er-rum or something similar. Juveniles are green with many scattered small black dots on the back. In large larvae, the upper surface is green with small black sharp-edged dots (and on tail fin), whereas the upper side is black with gold crossbands in individuals less than one inch (2.5 cm) long. Maximum length of larvae is about 7 inches (18 cm); commonly they are 4 inches long or longer (10+ cm). Eggs are black above, whitish below, deposited in flat jelly masses up to more than 1 meter in diameter and containing thousands of eggs (mass initially floats at surface of water but soon sinks). Source: Hammerson (1999).

American bullfrogs inhabit ponds, swamps, lakes, reservoirs, marshes, brackish ponds (e.g., Hawaii), stream margins, and irrigation ditches, especially sites with abundant floating, emergent, or submerged vegetation. They may disperse from water in wet weather and sometimes are found in temporary waters hundreds of meters from permanent water. Bullfrogs sometimes make seasonal migrations to and from ephemeral bodies of water, or between adjacent permanent aquatic habitats. Individuals often remain in one pond or in a cluster of adjacent ponds throughout a season but may move up to a mile or more from one year to the next. Breeding sites are primarily permanent slow- or nonflowing bodies of water.

Introduced bullfrogs apparently have detrimental effects on populations of native ranid frogs.

Bullfrog larvae generally are not palatable to fish predators but are sensitive to invertebrate predators (e.g., see Smith et al. 1999).

Bullfrogs in hand may go limp, then suddenly "revive" and leap away. Sometimes they produce a loud open-mouthed call lasting up to several seconds.

Breeding occurs when water temperatures are relatively warm, mainly in May-July in the northern part of the range, primarily late spring to late summer in Georgia, and mainly March through summer in Louisiana. Individual females produce 1-2 clutches/year. Larvae hatch in 4-20 days. In most areas, larvae overwinter at least once before metamorphosing, but larvae metamorphose in less than a year in warm climates (e.g., 5-6 months in Louisiana; less than 6 months in Hawaii, Tinker 1941). Individuals become sexually mature an average of 1-5 years after metamorphosis, with the oldest ages of maturity occurring in environments with the shortest growing seasons (e.g., average of 5 years after metamorphosis in central Ontario females); in a particular location, males tend to mature a year or so earlier than do females (Shirose et al. 1993).