American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae, Genus Lithobates, Species Lithobates catesbeianus. True frogs (Ranidae) are characterized by strong, long hind legs for leaping, smooth skin, and webbed feet.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae, Genus Lithobates, Species Lithobates catesbeianus. True frogs (Ranidae) are characterized by strong, long hind legs for leaping, smooth skin, and webbed feet.
Size
Snout-to-vent length (SVL) ranges from 90 to 200 mm (3.5 to 8 inches), occasionally up to 250 mm. Females are typically slightly larger than males. Weight can reach up to 500 grams or more, making it the largest frog in North America.
Conservation
IUCN Red List status is Least Concern with a stable population trend. However, they are considered a major invasive species outside their native range, threatening native biodiversity.
Description
The American Bullfrog is an impressive amphibian known for its massive size and booming, bass-heavy call. As a voracious apex predator of the wetlands, it commands attention sitting quietly at the water's edge, ready to launch into a powerful aquatic escape.
Key Features
Large size, absence of dorsolateral folds on the back, a circular fold looping around the large tympanum, and completely webbed hind feet.
Physical Description
Robust, stout body shape with a broad flat head. Large prominent eyes with a golden-brown iris and horizontal round pupil. A very large, circular tympanum (eardrum) is clearly visible behind the eye, larger in males. Limbs are muscular with extensive webbing on the hind feet, but lacking expanded toe pads. Dorsolateral folds are absent down the back, instead curving around the tympanum.
Skin Texture & Coloration
Dorsal skin is relatively smooth to slightly granular, featuring shades of olive green, brown, or grayish-green, often with dark mottling or spots. Ventral side is yellowish-white, sometimes with grey mottling. No warning coloration.
Distinguishing Features
Absence of dorsolateral folds along the back (unlike Green Frogs or Leopard Frogs), prominent circular fold curving around the large tympanum, and massive size as an adult.
Habitat
Found in large, permanent bodies of fresh water such as marshes, ponds, lakes, and slow-moving streams with abundant emergent aquatic vegetation.
Geographic Range
Native to eastern and central North America, stretching from southern Canada down to the Gulf of Mexico and east of the Great Plains. Extensively introduced worldwide, including parts of western North America, South America, Western Europe, and Asia.
Behavior
Primarily nocturnal and crepuscular, though active during the day in warm, overcast weather. Highly aquatic and territorial. When threatened, they emit a sudden loud squeak or jump directly into deep water.
Diet & Feeding
Generalist apex predator of the pond ecosystem. Eats virtually anything it can swallow, including insects, spiders, fish, snakes, birds, rodents, and other frogs using a sit-and-wait ambush strategy.
Reproduction
Breeds from late spring to mid-summer, triggered by warm water temperatures and heavy rains. Males establish territories and call to attract females. Females lay massive surface films containing up to 20,000 eggs.
Vocalizations
Famous deep, resonant, foghorn-like call ('jug-o-rum') that can carry for up to a mile across open water, usually heard at night during summer.
Life Cycle
Eggs hatch in 3 to 5 days into large olive-green tadpoles. The larval stage typically lasts 1 to 2 years (sometimes up to 3 years in northern ranges) before undergoing metamorphosis into froglets. Total lifespan in the wild is 7 to 10 years.
Conservation Status
IUCN Red List status is Least Concern with a stable population trend. However, they are considered a major invasive species outside their native range, threatening native biodiversity.
Toxicity & Defense
Non-toxic to humans, though skin secretions can taste unpalatable to mammalian predators. Defense mechanisms rely on explosive leaping into water, camouflage, and startling predators with a loud distress squeak.
Ecological Role
Acts as an apex predator in aquatic food webs, controlling insect and small vertebrate populations while serving as prey for wading birds, fish, and mammals.
Similar Species
Green Frog (Lithobates clamitans), which possesses prominent dorsolateral folds running down the back and is significantly smaller.
Observation Tips
Best observed at night along the edges of ponds or lakes using a flashlight, where their reflective eye shine gives away their location. Listen for the booming male calls during warm summer evenings.
Handling & Safety
Safe to handle, but should be done with wet hands to protect their sensitive skin from oils, soaps, and chemical residues. They can deliver a strong grip or thrash vigorously when caught.
Seasonal Activity
Active from spring through autumn. Overwinters (brumates) by burrowing into the mud at the bottom of ponds and lakes during freezing winter months.
Cultural Significance
Frequently featured in folklore, literature (such as Mark Twain's famous jumping frog story), and popular culture. Also widely farmed for food (frog legs).
Interesting Facts
Bullfrogs are known to eat almost any living creature smaller than themselves, including small turtles and bats. Their tadpoles can grow much larger than the adults of smaller frog species.