American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. Ranids are known for powerful hind legs and smooth, moist skin.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. Ranids are known for powerful hind legs and smooth, moist skin.
Size
The largest frog in North America. Adults typically reach 3.6 to 6 inches (9 to 15 cm) in SVL, weighing up to 1.1 lbs (500g). Females are generally larger than males.
Conservation
IUCN Status: Least Concern. Populations are stable or increasing, largely due to their ability to adapt to human-disturbed habitats and their status as an invasive species outside their native range.
Description
An iconic North American giant, the American Bullfrog is a titan of the wetlands. With its powerful build and deep, thrumming voice, it dominates the shoreline. Seeing one requires a keen eye, as their muddy green skin blends perfectly with algae and murky water.
Key Features
Large size, absence of dorsolateral folds along the back, and a distinct fold of skin that wraps around the large circular tympanum.
Physical Description
A highly robust and large-bodied frog. Features a broad, flat head, large gold-to-brown eyes with horizontal pupils, and a very prominent tympanum (eardrum) located just behind the eye. Lacks dorsolateral ridges extending down the back, instead possessing a ridge that curves around the eardrum down toward the shoulder.
Skin Texture & Coloration
Skin is generally smooth but can have small tubercles. Dorsal color ranges from dull olive green to brown with darker mottling. The belly is white or cream, often with grey mottling. The throat of the male is often yellow during breeding season. Does not possess aposematic coloration.
Distinguishing Features
The lack of dorsolateral folds (ridges) extending to the hips is the primary diagnostic marker; the ridge only curves around the tympanum. The tympanum is as large as or larger than the eye (significantly larger in males). Features fully webbed hind toes except for the fourth toe.
Habitat
Found in permanent bodies of water such as ponds, lakes, marshes, and slow-moving streams. Prefers areas with abundant aquatic vegetation for cover and hunting. Highly aquatic but will move over land during rainy nights.
Geographic Range
Native to eastern and central North America (US and Canada). It has been widely introduced to the western US, Europe, Asia, and South America, where it is often considered a highly invasive species.
Behavior
Primarily nocturnal but active during the day near water edges. Highly territorial; males engage in physical wrestling. Possesses a powerful leap and is a strong swimmer. Known for a 'screaming' startle response when threatened.
Diet & Feeding
Voracious, opportunistic predators. They eat almost anything they can swallow: insects, crayfish, other frogs, rodents, small birds, snakes, and fish. They use a 'sit-and-wait' ambush strategy.
Reproduction
Breeding occurs in late spring to summer. Amplexus is axillary. Females lay up to 20,000 eggs in large floating masses. Mating involves loud choruses of territorial males.
Vocalizations
A deep, resonant basso 'jug-o-rum' or 'rum-rum-rum.' The call can carry for over half a mile and sounds like a distant lowing bull. Useful for identification from a distance.
Life Cycle
Eggs hatch in 3-5 days. The tadpole stage is exceptionally long, lasting 1 to 3 years depending on climate. Tadpoles are large and olive-green. Metamorphosis results in a juvenile that reaches maturity in 2-4 years. Lifespan is 7-9 years in the wild.
Conservation Status
IUCN Status: Least Concern. Populations are stable or increasing, largely due to their ability to adapt to human-disturbed habitats and their status as an invasive species outside their native range.
Toxicity & Defense
Not toxic to humans. Defensive strategies include camouflage, huge leaps into water, and inflating the body to appear larger. Skin secretions may be unpalatable to some predators.
Ecological Role
Top-tier amphibian predator. Helps control insect and crustacean populations but can decimate local native frog populations where it is introduced.
Similar Species
Green Frog (Lithobates clamitans), which has prominent dorsolateral ridges extending down at least half the back; River Frog (Lithobates heckscheri), which has a darker belly and lacks the specific tympanum fold.
Observation Tips
Scan shorelines at night using a flashlight; their eyes reflect a bright gold eyeshine. Listen for the deep 'jug-o-rum' call during warm summer nights near permanent water.
Handling & Safety
Generally safe to handle with wet hands to protect their slime coat. Wash hands afterward to avoid Salmonella. Avoid handling if you have lotions or insect repellent on your skin.
Seasonal Activity
Active from spring through autumn. In colder climates, they hibernate underwater, buried in the mud at the bottom of ponds where they absorb oxygen through their skin.
Cultural Significance
A staple of American folklore and early natural history writing. Often depicted in popular culture as the quintessential 'pond frog.' Used heavily in biology classrooms for dissection.
Interesting Facts
The American Bullfrog has been known to eat bats and small birds. They are the official state amphibian of Missouri, Ohio, and Oklahoma. They are also farmed globally for frog legs.