American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species catesbeianus. They are the largest true frogs in North America.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species catesbeianus. They are the largest true frogs in North America.
Size
Adults can reach a snout-to-vent length (SVL) of 3.6 to 6 inches, with some reaching 8 inches. The juvenile in the image appears to be approximately 1.5 to 2 inches SVL. Females are generally larger than males.
Conservation
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are a primary threat to native amphibians due to predation and competition.
Description
The American Bullfrog is the heavyweight champion of North American ponds. This juvenile specimen represents the early stages of a creature that will grow into a massive, emerald-green predator. Seeing one in the wild is a classic summer experience, usually punctuated by their deep, booming choruses and the splash of their impressively long jumps.
Key Features
Absence of dorsolateral folds, large tympanum (eardrum), ridge wrapping behind the ear, fully webbed hind toes.
Physical Description
A robust, large-bodied frog with a Broad, flat head. It features a large visible tympanum (eardrum) behind the eye and lacks dorsolateral folds running down the back (unlike Green Frogs). Limbs are powerful with fully webbed hind feet.
Skin Texture & Coloration
Skin is generally smooth but can have small tubercles. Dorsal color ranges from bright green to olive or brown, often with dark mottling. The belly is white or yellowish. Juveniles, like the one pictured, often show more distinct spotting.
Distinguishing Features
The most definitive field mark is the absence of dorsolateral folds; instead, a ridge runs from the back of the eye, circles behind the tympanum, and ends at the shoulder. Large tympanum is equal to or larger than the eye.
Habitat
Highly aquatic; found in permanent bodies of water such as ponds, lakes, marshes, and sluggish streams with abundant vegetation. They prefer warm, shallow water for breeding.
Geographic Range
Native to central and eastern North America. However, they have been widely introduced to western North America, South America, Europe, and Asia, where they are often invasive.
Behavior
Primarily nocturnal but active during the day in warm weather. They are sit-and-wait predators and are known for their aggressive territoriality. If startled, they often leap into water while emitting a short 'yip' or squeak.
Diet & Feeding
Voracious opportunistic carnivores. They eat insects, crayfish, worms, and notably, vertebrates like other frogs, small fish, snakes, turtles, birds, and even bats. They use a powerful tongue and strong jaws.
Reproduction
Breeding occurs in late spring to summer. Males establish territories and call loudly. Females lay up to 20,000 eggs in large floating masses. Amplexus is axillary (behind the front arms).
Vocalizations
A deep, resonant, bass-like 'jug-o-rum' or 'br-wum' that can be heard from over a kilometer away. It sounds like a low-pitched bellows or a distant foghorn.
Life Cycle
Eggs hatch in 3-5 days. The tadpole stage is exceptionally long, often lasting 1 to 2 years (shorter in the south, longer in the north). Metamorphosis results in a froglet that takes 2-3 years to reach sexual maturity.
Conservation Status
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are a primary threat to native amphibians due to predation and competition.
Toxicity & Defense
Not toxic to humans, but their skin secretions can be unpalatable to some predators. Principal defenses include camouflage, powerful leaping ability, and large size as adults.
Ecological Role
Apex predator among amphibians; they control insect and small vertebrate populations but can disrupt ecosystems where they are invasive by eating native species.
Similar Species
Green Frog (Lithobates clamitans), which has prominent dorsolateral folds extending at least halfway down the back. Mink Frog (Lithobates septentrionalis), which has a more mottled appearance and skin that smells like musk.
Observation Tips
Scan the edges of ponds using a flashlight at night to catch 'eye shine.' During the day, look for their heads poking above the surface of floating vegetation or sitting at the water's edge.
Handling & Safety
Safe to handle, but always wet your hands first to protect their permeable skin. Avoid contact with soap, lotion, or bug spray. Wash hands thoroughly after handling to prevent potential salmonella exposure.
Seasonal Activity
Active from early spring until the first frosts. They hibernate (brumate) underwater, buried in the mud at the bottom of ponds where they can survive through gas exchange through their skin.
Cultural Significance
A staple of American folklore and biology classrooms. Famous in literature (Mark Twain's 'The Celebrated Jumping Frog of Calaveras County') and an indicator of permanent water sources.
Interesting Facts
The 'Bull' in their name refers to their call sounding like a roaring bull. They are the state amphibian of Missouri, Ohio, and Oklahoma. They are also farmed for their legs as a food source.