American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. They are characterized as large, aquatic frogs with powerful hind legs and fully webbed feet.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates, Species L. catesbeianus. They are characterized as large, aquatic frogs with powerful hind legs and fully webbed feet.
Size
The largest frog in North America. SVL typically ranges from 3.5 to 6 inches (9-15 cm), but can reach 8 inches (20 cm). Adults weigh between 0.5 to 1.8 lbs. Females are generally larger than males.
Conservation
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are a threat to biodiversity as an invasive species that outcompetes and consumes native amphibians.
Description
An iconic giant of the North American wetlands. The Bullfrog is the quintessential 'pond frog,' often seen basking on lily pads or at the water's edge. Its deep drone is a staple of summer nights, signifying a healthy, albeit hungry, aquatic ecosystem.
Key Features
Large size (over 4 inches), lack of dorsolateral folds along the back, a fold of skin curving around the large tympanum, and a bright green snout.
Physical Description
A robust, heavy-bodied frog with a large, broad head. It features large gold or brown eyes with horizontal pupils and a distinct, very large circular tympanum (eardrum) located just behind the eye. Limbs are thick and powerful, particularly the hind legs.
Skin Texture & Coloration
Skin is generally smooth but can have small tubercles. Dorsal color ranges from olive green to brownish-drab with darker grey or brown mottling. The upper lip and snout often show a bright green wash. The venter is creamy white, often with grey mottling. No warning coloration is present.
Distinguishing Features
Crucially, it lacks dorsolateral folds (ridges) extending down the back; instead, a conspicuous ridge runs from behind the eye and curves around the tympanum. In males, the tympanum is significantly larger than the eye, whereas in females, it is about the same size.
Habitat
Highly aquatic; found in permanent bodies of water such as lakes, ponds, sluggish rivers, and marshes. They prefer areas with abundant aquatic vegetation and warm water. Elevation ranges from sea level to mid-montane regions.
Geographic Range
Native to central and eastern North America. However, it has been widely introduced to the western United States, South America, Europe, and Asia, where it is often considered a highly invasive species.
Behavior
Primarily nocturnal but active during the day. They are sit-and-wait predators. When threatened, they leap into water with a short 'yip' sound. They are highly territorial, and males will engage in wrestling bouts during the breeding season.
Diet & Feeding
Voracious opportunistic carnivores. They eat anything they can swallow, including insects, crayfish, worms, fish, turtles, snakes, birds, bats, and other frogs (including their own species). They use a powerful tongue projection and 'eye-blinking' to help push prey down.
Reproduction
Breeding occurs in late spring to summer. Males form choruses to attract females. Amplexus is axillary. Females lay up to 20,000 eggs in large floating film mats on the water surface. No parental care is provided after egg laying.
Vocalizations
The distinctive call is a deep, resonant, bass 'jug-o-rum' or 'br-wum'. It can be heard from long distances. Males also produce a sharp 'hiccup' territorial call and a high-pitched scream when startled or seized by a predator.
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 with black spots. Metamorphosis occurs in summer, and sexual maturity is reached in 2-4 years. Wild lifespan is 7-9 years.
Conservation Status
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are a threat to biodiversity as an invasive species that outcompetes and consumes native amphibians.
Toxicity & Defense
Not toxic to humans. Defense relies on camouflage, large size, powerful leaps into water, and a slippery mucus coating that makes them difficult for predators to hold.
Ecological Role
Top-tier aquatic predator in the amphibian world. They control insect populations but can disrupt ecosystems when introduced by preying on smaller endangered species. Tadpoles help control algae.
Similar Species
Green Frog (Lithobates clamitans): Very similar but has prominent dorsolateral folds running halfway down the back. Mink Frog (L. septentrionalis): Smaller with a more mottled pattern and musky odor.
Observation Tips
Visit permanent ponds on warm summer nights with a flashlight. Scan the water's edge for reflecting 'eyeshine'. They are most vocal and visible during the peak heat of June and July.
Handling & Safety
Safe to handle, but they are powerful and may kick. Always have wet hands to protect their skin. They can carry Salmonellosis and the Chytrid fungus, so wash hands thoroughly after contact. Legal to catch in many states with a fishing license.
Seasonal Activity
Active from early spring through autumn. They overwinter (brumate) in the mud at the bottom of ponds that do not freeze solid. They emerge when water temperatures consistently stay above 60°F.
Cultural Significance
Commonly featured in American folklore and literature (Mark Twain's 'The Celebrated Jumping Frog of Calaveras County'). They represent summer and wetlands in popular media.
Interesting Facts
The Bullfrog is the state amphibian of Missouri, Ohio, and Oklahoma. They are famous for 'frog jumping' contests and are the primary species used in the culinary industry for frog legs.