American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. They are typical 'true frogs' characterized by powerful hind legs and smooth or granular skin.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. They are typical 'true frogs' characterized by powerful hind legs and smooth or granular skin.
Size
The largest frog in North America, with a standard SVL of 3.5 to 8 inches (9-20 cm). Adults can weigh up to 1.1 lbs (0.5 kg). Females are generally larger than males.
Conservation
IUCN status: Least Concern. Populations are stable and expanding in some areas. The primary threat is habitat pollution, though they are highly resilient and their invasive presence is a threat to other amphibians.
Description
The American Bullfrog is the quintessential pond dweller of North America, an imposing figure of olive and gold. It sits motionless amongst vegetation, a master of patience and power, waiting for any movement that suggests a meal. Its presence is defined by the guttural symphony it creates on warm summer nights.
Key Features
Massive size; Large tympanum; Ridge that wraps around the ear rather than running down the back; Fully webbed toes.
Physical Description
A very large, robust frog with a broad, flat head. It features prominent, large eyes and exceptionally large tympana (eardrums) located just behind and below the eyes. The limbs are powerful with fully webbed hind feet. It lacks dorsolateral folds except for a short ridge that curves around the eardrum.
Skin Texture & Coloration
Skin is granular and slightly bumpy but lacks the dry warts of a toad. Coloration ranges from olive-green to brownish-yellow dorsally, while the belly is whitish with gray mottling. Males often have a bright yellow throat during breeding season. The specimen in the image shows a distinct yellowish-olive hue.
Distinguishing Features
The lack of continuous dorsolateral folds (ridges) running down the back is the primary diagnostic marker; the ridge instead folds sharply behind the tympanum. In males, the tympanum is significantly larger than the eye, whereas in females, it is about the same size.
Habitat
Highly aquatic; preferring permanent bodies of water including ponds, lakes, marshes, and slow-moving streams with abundant aquatic vegetation for cover.
Geographic Range
Native to central and eastern North America. However, it has been widely introduced across the western United States, Europe, South America, and Asia, where it is often considered an invasive species.
Behavior
Diurnal and nocturnal, but most active at night. They are highly territorial ambush predators. If startled, they often emit a high-pitched 'squeak' before jumping into the water for safety.
Diet & Feeding
Indiscriminate carnivores. They eat almost anything they can swallow: insects, crayfish, other frogs, snakes, turtles, rodents, and even small birds and bats. They use a sit-and-wait ambush strategy.
Reproduction
Occurs in late spring and summer. Males call in choruses to attract females. Females lay up to 20,000 eggs in large floating masses. Amplexus is axillary (grasping behind the front legs).
Vocalizations
A deep, resonant, bass-like 'jug-o-rum' or 'br-wum' that can carry for long distances. Often compared to the lowing of a bull, which gives the species its name.
Life Cycle
Egg masses hatch into tadpoles within 3-5 days. The tadpole stage is exceptionally long, lasting 1 to 3 years depending on the climate. Metamorphosis results in a juvenile that takes 2-3 years to reach sexual maturity.
Conservation Status
IUCN status: Least Concern. Populations are stable and expanding in some areas. The primary threat is habitat pollution, though they are highly resilient and their invasive presence is a threat to other amphibians.
Toxicity & Defense
Not toxic to humans, but produces skin secretions that are unpalatable to some predators. Their primary defense is their massive size, powerful leap, and camouflaged skin.
Ecological Role
As an apex predator in the amphibian world, they control insect and small vertebrate populations. However, in introduced ranges, they are devastating to local biodiversity due to their voracious appetites.
Similar Species
Green Frog (Lithobates clamitans), which is smaller and possesses distinct dorsolateral folds that run two-thirds of the way down the back.
Observation Tips
Look along the edges of permanent ponds at night using a flashlight. Their large eyes reflect light (eyeshine) brightly. Listen for the deep 'jug-o-rum' call on humid summer evenings.
Handling & Safety
Safe to handle but generally discouraged. Their skin is sensitive to chemicals on human hands. They have a very strong grip and may attempt to bite if they mistake a finger for prey, which can be painful but is not dangerous.
Seasonal Activity
Active from May through September in northern regions; year-round in southern, warmer climates. They hibernate in the mud at the bottom of ponds during winter.
Cultural Significance
A staple of American folklore and biological education. It is frequently the 'frog in a jar' for students first learning biology and represents a symbol of summer in rural North America.
Interesting Facts
The Bullfrog is the state amphibian of several US states, including Missouri and Ohio. They are also farmed globally for their legs, which are a culinary delicacy.