American Bullfrog (Lithobates catesbeianus)
Order Anura, Family Ranidae (True Frogs), Genus Lithobates. They are characterized by smooth skin, long legs, and a strong association with permanent water bodies.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order Anura, Family Ranidae (True Frogs), Genus Lithobates. They are characterized by smooth skin, long legs, and a strong association with permanent water bodies.
Size
The largest frog in North America. SVL typically ranges from 3.5 to 6 inches (9–15 cm), but can reach 8 inches. Females are generally larger than males. They can weigh up to 1.1 lbs (0.5 kg).
Conservation
IUCN Status: Least Concern. Populations are stable and expanding in many areas due to human-mediated introduction, though they are a major threat to native biodiversity in non-native ranges.
Description
The American Bullfrog is the heavyweight of the North American amphibian world. A quintessential pond dweller, it is often seen floating at the water's surface with only its large, golden eyes and nostrils exposed, blending perfectly with pond scum and algae.
Key Features
Large size; green to olive-brown color; tympanum as large or larger than the eye; lack of dorsolateral folds on the back; ridge curving only around the eardrum.
Physical Description
A robust, large-bodied frog with a broad, flat head. Features a prominent, circular tympanum (eardrum) behind the eye. It lacks dorsolateral folds (ridges) along the back, instead having a fold that curves around the tympanum.
Skin Texture & Coloration
Skin is mostly smooth with some small tubercles. Dorsal color ranges from olive to lime green, often with some dark mottling. The underside is whitish or yellow. During breeding, males' throats often turn bright yellow.
Distinguishing Features
The most diagnostic feature is the absence of dorsolateral folds extending down the back. Instead, a ridge runs from the eye, curves behind the tympanum, and ends at the shoulder. In males, the tympanum is much larger than the eye.
Habitat
Highly aquatic; found in permanent bodies of water such as ponds, lakes, marshes, and slow-moving streams. Prefers areas with abundant aquatic vegetation for cover.
Geographic Range
Native to central and eastern North America. However, it has been widely introduced across the western US, Europe, South America, and Asia, where it is often considered an invasive species.
Behavior
Primarily nocturnal but active during the day. Known for sit-and-wait hunting and aggressive territoriality. When startled, they often emit a short 'squeak' as they leap into the water.
Diet & Feeding
Indiscriminate predators. They eat insects, crayfish, fish, turtles, snakes, birds, bats, and even other frogs. They use a powerful 'flip-and-grab' tongue strike for smaller prey and lunging for larger items.
Reproduction
Breeding occurs in late spring and summer. Males form choruses to attract females. Females lay up to 20,000 eggs in large, floating mass 'rafts' in shallow water. Amplexus is axillary.
Vocalizations
A deep, resonant, bass-like 'jug-o-rum' or 'br-wum' that can carry for over a kilometer. It resembles the lowing of a bull, which is the source of its common name.
Life Cycle
Eggs hatch in 3–5 days. The tadpole stage is exceptionally long, lasting 1 to 3 years depending on the climate. Adults can live 7–10 years in the wild and longer in captivity.
Conservation Status
IUCN Status: Least Concern. Populations are stable and expanding in many areas due to human-mediated introduction, though they are a major threat to native biodiversity in non-native ranges.
Toxicity & Defense
Not toxic to humans. Defenses include camouflage, powerful leaping ability to escape into water, and the ability to inflate their bodies to appear larger to predators.
Ecological Role
Top-tier pond predator and prey for herons, raccoons, and large fish. In their invasive range, they are devastating to native ecosystems as they outcompete and eat local species.
Similar Species
Green Frog (Lithobates clamitans), which has distinct dorsolateral folds running two-thirds down the length of the back. Pig Frog (Lithobates grylio), which has more pointed snout and fully webbed toes.
Observation Tips
Look for them at the edges of ponds on warm summer nights using a flashlight (their eyes reflect brilliantly). Listen for the deep 'jug-o-rum' call during the breeding season.
Handling & Safety
Safe for humans but stressful for the frog. Always wash hands after handling to prevent the spread of bacteria. Human skin oils and salts can irritate their permeable skin.
Seasonal Activity
Active from late spring through early autumn. They hibernate in the winter at the bottom of ponds, buried in mud or debris, where they can survive under ice.
Cultural Significance
Commonly featured in literature (Mark Twain's 'The Celebrated Jumping Frog of Calaveras County') and once a primary source for the 'frog legs' culinary trade.
Interesting Facts
Bullfrogs are famous for their jumping ability, capable of leaping distances up to 3–6 feet. They are also 'living fossils' of a sort, with a general body plan that has remained successful for millions of years.