American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae, Genus Lithobates, Species Lithobates catesbeianus
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae, Genus Lithobates, Species Lithobates catesbeianus
Size
Adult snout-to-vent length (SVL) typically ranges from 90 to 152 mm, with exceptionally large individuals reaching up to 200 mm. Females are generally larger than males. Weight can range from 300 to 500 grams or more.
Conservation
IUCN Red List status is Least Concern, with a stable population trend. However, they are considered an invasive species in regions outside their native range.
Description
The American Bullfrog is a large and powerful amphibian, perfectly adapted to a semi-aquatic lifestyle. With its deep, resonant call echoing across wetlands, it stands out as an iconic master ambush predator of North American waters.
Key Features
Large size, absence of dorsolateral folds, large circular eardrum (tympanum), and olive-green mottled dorsal coloration.
Physical Description
Robust, stout-bodied frog with a broad, flat head, prominent eyes with golden irises and horizontal pupils, highly visible circular tympanums behind the eyes, strong muscular hind limbs with extensive webbing on the toes, and lack of dorsolateral folds on the back.
Skin Texture & Coloration
Skin is relatively smooth to slightly granular, particularly on the back and legs. Coloration ranges from olive green to shades of brown or gray on the dorsal side, heavily mottled or speckled with darker spots and blotches. The ventral side is yellowish-white, often mottled with gray or brown.
Distinguishing Features
Absence of dorsolateral folds along the back, very large circular tympanums (larger than the eye in mature males), and a fold of skin that wraps around the tympanum down to the shoulder.
Habitat
Found primarily in permanent freshwater bodies such as large ponds, lakes, swamps, and slow-moving rivers with abundant aquatic vegetation and muddy bottoms.
Geographic Range
Native to eastern and central North America, ranging from southern Canada down to the Gulf of Mexico, and widely introduced across western North America, South America, Europe, and Asia.
Behavior
Predominantly nocturnal and aquatic, sitting motionless near the water's edge ready to plunge in when disturbed. Highly territorial during the breeding season.
Diet & Feeding
Opportunistic apex ambush predator consuming insects, small fish, crayfish, snakes, birds, rodents, and other frogs.
Reproduction
Breeds in late spring and summer in shallow permanent waters. Males establish territories and emit loud calls to attract females, who lay large surface films of up to 20,000 eggs.
Vocalizations
Deep, resonant, foghorn-like call ('jug-o-rum') that can carry for long distances over water.
Life Cycle
Eggs hatch in a few days into large, olive-green tadpoles that may take one to three years to metamorphose into juveniles, with a total lifespan in the wild of 7 to 10 years.
Conservation Status
IUCN Red List status is Least Concern, with a stable population trend. However, they are considered an invasive species in regions outside their native range.
Toxicity & Defense
Non-toxic to humans, relying instead on rapid swimming into deep water, powerful jumps, and camouflage, combined with defensive distress calls.
Ecological Role
Acts as an apex predator in aquatic food webs, controlling insect and small vertebrate populations while serving as prey for larger wading birds, mammals, and fish.
Similar Species
Green Frog (Lithobates clamitans) and Pig Frog (Lithobates grylio). Green frogs possess dorsolateral folds that run down the back, unlike the bullfrog.
Observation Tips
Best observed at night near the edges of permanent ponds or lakes using a flashlight, looking for the reflective glint of their eyes.
Handling & Safety
Safe to handle with clean, wet hands, though large individuals can deliver a strong grip or release powerful squirts of urine. Care should be taken to avoid spreading pathogens.
Seasonal Activity
Active from spring through autumn, entering brumation (hibernation) at the bottom of ponds buried in mud during freezing winter months.
Cultural Significance
Frequently featured in literature, folklore, and popular culture, most notably in Mark Twain's famous short story about the jumping frog of Calaveras County.
Interesting Facts
The American Bullfrog is the largest frog species in North America and is capable of leaping up to ten times its body length in a single bound.