American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. This family is characterized by smooth, moist skin, large muscular legs, and fully webbed hind feet.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. This family is characterized by smooth, moist skin, large muscular legs, and fully webbed hind feet.
Size
The largest frog in North America. SVL typically 9–15 cm, but can reach 20 cm. Weight ranges from 300 to 500 grams. Females are generally larger than males. Tadpoles can grow up to 15 cm before metamorphosis.
Conservation
IUCN Status: Least Concern. Populations are stable and expanding in non-native ranges. Major threats include habitat degradation and pollution, but their adaptability makes them highly resilient.
Description
The American Bullfrog is the heavyweight champion of North American amphibians. With its iconic deep voice and emerald-to-mahogany complexion, it represents the classic 'pond frog.' It is an apex predator of the micro-world, commanding the water's edge with patience and explosive power.
Key Features
No dorsolateral folds; fold of skin only around the tympanum; large size; fully webbed hind toes except for the tip of the longest toe; large circular eardrum.
Physical Description
A very large, robust frog with a broad, flat head and a blunt snout. It features large, gold-to-hazel eyes and a prominent tympanum (external eardrum). The hind legs are powerful and long, while the front legs are short and stout. It lacks dorsolateral ridges running down the back beyond the tympanum.
Skin Texture & Coloration
Skin is generally smooth with some small tubercles. Dorsal color ranges from olive green to brownish-gray, often with dark mottling. The belly is white or cream, sometimes with yellow wash or gray marbling. Males often have a bright yellow throat during breeding season.
Distinguishing Features
Total absence of dorsolateral folds along the sides of the back; instead, a distinct ridge of skin wraps around the back of the tympanum. The tympanum is as large as or larger than the eye (larger in males).
Habitat
Highly aquatic; found in permanent bodies of water such as lakes, ponds, sluggish rivers, and marshes. They prefer areas with abundant vegetation for cover and warm, shallow water for breeding.
Geographic Range
Native to eastern and central North America (Canada and USA). Widely introduced across the western USA, Europe, Asia, and South America, where it is often considered a highly invasive species.
Behavior
Primarily nocturnal but active during the day. Known for aggressive territoriality; males defend calling sites via physical wrestling. They are sit-and-wait predators that will lunge at anything they can swallow.
Diet & Feeding
Generalist carnivore. Diet includes insects, crustaceans, fish, snakes, birds, bats, and other frogs (including their own species). They use a powerful tongue and strong jaws to secure large prey.
Reproduction
Late spring to early summer breeding. Males gather in choruses to attract females. Amplexus is axillary. Females lay up to 20,000 eggs in large, floating film-like masses on the water surface.
Vocalizations
A deep, resonant, two-note bass call described as 'jug-o-rum' or 'better-go-deep.' The call can be heard from over a kilometer away and serves as an advertisement for territory and mates.
Life Cycle
Eggs hatch in 3-5 days. The tadpole stage is exceptionally long, lasting 1 to 3 years depending on climate. Metamorphosis occurs in summer. Adults can live 8-10 years in the wild, longer in captivity.
Conservation Status
IUCN Status: Least Concern. Populations are stable and expanding in non-native ranges. Major threats include habitat degradation and pollution, but their adaptability makes them highly resilient.
Toxicity & Defense
Not toxic to humans. Defensive strategies include jumping into water with a loud 'peep' or splash, inflating the body to appear larger, and potentially biting with strong jaws if handled aggressively.
Ecological Role
Functions as both a major predator and a significant prey source for herons and raccoons. In invasive ranges, they cause ecological collapse by outcompeting and eating native amphibian species.
Similar Species
Green Frog (Lithobates clamitans), which possesses prominent dorsolateral folds extending down two-thirds of the back; Pig Frog (Lithobates grylio), which has more pointed snout and fully webbed toes.
Observation Tips
Look along the muddy edges of permanent ponds on warm summer nights. Their eyes reflect light (eyeshine) clearly under a flashlight beam. Listen for the 'jug-o-rum' call at dusk.
Handling & Safety
Safe for humans but should be handled with wet hands to protect their semi-permeable skin. Large adults have strong grips and may attempt to bite, which can be surprising but is not dangerous.
Seasonal Activity
Active from spring through autumn. In colder climates, they hibernate underwater, buried in the mud at the bottom of ponds where they breathe through their skin.
Cultural Significance
Famous in literature through Mark Twain's 'The Celebrated Jumping Frog of Calaveras County.' They are also a traditional food source (frog legs) in French and Southern American cuisine.
Interesting Facts
Bullfrogs are famous for their jumping ability, capable of leaping 1-2 meters. They are also known to hunt and eat small birds and hatchling turtles, making them unique among North American frogs for their vertebrate-heavy diet.