American Bullfrog (Lithobates catesbeianus)

Order: Anura, Family: Ranidae (True Frogs), Genus: Lithobates, Species: L. catesbeianus. This species is the largest member of the family Ranidae in North America, characterized by powerful hind legs and large tympana.

Species

Family

Size

The largest frog in North America, reaching a snout-to-vent length (SVL) of 3.6 to 6 inches (9 to 15 cm), with some reaching 8 inches. They can weigh up to 1.1 lbs (0.5 kg). Females are typically larger than males.

Conservation

IUCN Status: Least Concern. Population is stable and expanding in non-native ranges. They are often considered a threat to local biodiversity in areas where they are introduced due to predation and disease spread.

Description

The American Bullfrog is a quintessential icon of North American wetlands. With its deep, booming voice and impressive size, it commands the edge of the pond. In the grass, as seen in the image, its mottled brown and green skin provides excellent camouflage against both vegetation and mud.

Key Features

Large size, absence of dorsolateral folds on the back, and a skin ridge that wraps around the large eardrum (tympanum).

Physical Description

A robust, large-bodied frog with a wide, blunt head. It features large, prominent eyes with horizontal pupils and a conspicuous external eardrum (tympanum). The hind limbs are long and muscular with extensive webbing on the toes, while the front limbs are shorter. It lacks dorsolateral folds that run down the back, which is a key trait.

Skin Texture & Coloration

Skin is generally smooth but can have small tubercles. Dorsal color ranges from olive green to brownish; the specimen in the image shows a yellowish-brown mottled pattern. The belly is typically cream or white, often with gray mottling. It does not possess aposematic coloration but relies on cryptic camouflage.

Distinguishing Features

The most definitive feature is the absence of dorsolateral folds along the back; instead, a ridge of skin runs from the eye, behind the tympanum, and curves down toward the shoulder. The tympanum is as large as or larger than the eye (larger in males).

Habitat

Primarily aquatic; found in permanent bodies of water such as lakes, ponds, sluggish streams, and marshes. They prefer areas with abundant aquatic vegetation for cover. Highly adaptable to man-made environments like farm ponds and canals.

Geographic Range

Native to eastern North America from southern Canada to Florida. However, they have been widely introduced to the western United States, Europe, South America, and Asia, where they often become an invasive species.

Behavior

Primarily nocturnal and crepuscular, though they bask during the day. They are highly territorial, especially males during breeding. They are known for being sit-and-wait predators and are powerful swimmers. When startled, they may emit a 'squeak' as they leap into water.

Diet & Feeding

Generalist carnivores with a 'gape-limited' diet. They eat anything they can swallow: insects, crayfish, other frogs, fish, turtles, snakes, birds, and small mammals. Their tongue is attached at the front of the mouth and flips out to catch prey.

Reproduction

Breeding occurs in late spring to summer. Males establish territories and call to attract females. Amplexus is axillary. A single female can lay up to 20,000 eggs in a floating mass. Tadpoles are large and may take 1 to 3 years to reach metamorphosis.

Vocalizations

The advertisement call is a deep, resonant, multi-note 'jug-o-rum' or 'br-wum' that can be heard from over a half-mile away. It sounds like a low-pitched bass fiddle. Males also produce a 'warm-up' stutter before the full call.

Life Cycle

Eggs hatch in 3-5 days. Tadpoles are olive-green with black dots and can grow up to 6 inches before metamorphosing. Metamorphosis involves growing limbs and losing the tail. Sexual maturity is reached in 2-4 years. Lifespan in the wild is 7-10 years.

Conservation Status

Toxicity & Defense

While not toxic to humans, they produce mild skin secretions that make them unpalatable to some predators. Their primary defense is their powerful jump, large size, and loud distress vocalizations.

Ecological Role

Top-tier amphibian predators that control insect and small vertebrate populations. However, as an invasive species, they can decimate local populations of native frogs and turtles. They are an important food source for herons and raccoons.

Similar Species

Green Frog (Lithobates clamitans), which looks similar but has prominent dorsolateral folds running two-thirds down the length of its back. Leopard Frogs have distinct circular spots and folds.

Observation Tips

Listen for the 'jug-o-rum' call at night during summer months. Scan the edges of ponds with a flashlight; their large eyes have a bright green/yellow eye-shine. Approach slowly as they are very wary.

Handling & Safety

Generally safe to handle, but wet hands first to protect their permeable skin. They have powerful legs and may struggle. Humans should wash hands after contact to avoid Salmonella. Avoid handling if you have lotions or insect repellent on your skin.

Seasonal Activity

In temperate regions, they hibernate in the mud at the bottom of ponds during winter. They emerge in spring as water temperatures rise, becoming most active and vocal during the peak heat of summer.

Cultural Significance

Famous in American literature (e.g., Mark Twain's 'The Celebrated Jumping Frog of Calaveras County') and popular songs ('Jeremiah was a bullfrog'). They symbolize both the charm and the predatory nature of the swamp.

Interesting Facts

Bullfrogs are known to stay in the tadpole stage for several years in northern climates. They are the official state amphibian of Missouri, Ohio, and Oklahoma. They are also famous for 'frog leg' cuisine.

Identified on 6/27/2026