American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae, Genus Lithobates, Species L. catesbeianus
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae, Genus Lithobates, Species L. catesbeianus
Size
Snout-to-vent length ranges from 90 to 150 mm (exceptionally up to 200 mm). Females are typically slightly larger than males. Weight ranges from 300 to over 500 grams.
Conservation
IUCN status is Least Concern with a stable population trend. They are considered invasive in many regions outside their native range.
Description
The American Bullfrog is the largest frog native to North America. With its commanding presence, deep bass call, and voracious appetite, it is an iconic species of permanent wetlands and ponds.
Key Features
Large size, absence of dorsolateral folds, enormous tympanum behind the eye, and bright green upper jaw.
Physical Description
Robust, stout body with a broad head, prominent large circular tympanums just behind the eyes, golden-to-brown horizontal pupils, strong muscular hind legs, and extensive webbing on the hind toes.
Skin Texture & Coloration
Skin is relatively smooth to slightly granular dorsally. Coloration ranges from olive-green to dark brown, often featuring dark spots, mottling, or reticulations. The upper lip and jaw area frequently exhibit a bright green coloration, particularly in males.
Distinguishing Features
Absence of dorsolateral folds along the back (unlike the green frog), a very large tympanum (larger than the eye in mature males), and prominent green coloration on the upper jaw.
Habitat
Found in permanent freshwater bodies such as large ponds, lakes, marshes, and slow-moving streams with abundant aquatic vegetation and muddy bottoms.
Geographic Range
Native to eastern and central North America, but widely introduced across western North America, parts of South America, Asia, and Europe.
Behavior
Primarily nocturnal and aquatic. Highly territorial, sit-and-wait predators. When threatened, they dive deeply into water or emit a loud distress call.
Diet & Feeding
Opportunistic carnivores feeding on insects, spiders, small fish, snakes, birds, rodents, and other frogs. Uses a sticky tongue and powerful jaws to capture prey.
Reproduction
Breeds in late spring and summer. Males establish breeding territories and call loudly. Females deposit massive egg masses (up to 20,000 eggs) in surface films on the water.
Vocalizations
Deep, resonant, fog-horn-like 'jug-o-rum' call emitted by males during the breeding season.
Life Cycle
Eggs hatch in several days into large, olive-green tadpoles that may take one to three years to undergo metamorphosis into juveniles.
Conservation Status
IUCN status is Least Concern with a stable population trend. They are considered invasive in many regions outside their native range.
Toxicity & Defense
Non-toxic to humans, relying on jumping into water, cryptic coloration, and loud startling calls to evade predators.
Ecological Role
Acts as both a top aquatic predator controlling insect and amphibian populations and as prey for large fish, wading birds, and mammals.
Similar Species
Green Frog (Lithobates clamitans) and Pig Frog (Lithobates grylio). Distinguished primarily by the presence of dorsolateral folds in green frogs and size/geographical distribution.
Observation Tips
Best observed at night near the edges of permanent ponds using a flashlight to catch the ruby-red eye shine.
Handling & Safety
Safe to handle with wet hands, though large individuals can deliver a strong grip; care must be taken to avoid spreading pathogens between water bodies.
Seasonal Activity
Active from spring through autumn, brumating at the bottom of ponds during the winter months.
Cultural Significance
Frequently featured in folklore, literature (such as Mark Twain's famous jumping frog story), and widely harvested for human consumption (frog legs).
Interesting Facts
Bullfrogs are voracious predators that will attempt to eat almost any animal they can fit into their mouths, including bats, small turtles, and ducklings.