American Bullfrog (Lithobates catesbeianus)
Order: Anura; Family: Ranidae (True Frogs); Genus: Lithobates; Species: L. catesbeianus. Ranids are characterized by smooth, moist skin, large eardrums, and powerful hind legs for swimming.
Species
American Bullfrog (Lithobates catesbeianus)
Family
Order: Anura; Family: Ranidae (True Frogs); Genus: Lithobates; Species: L. catesbeianus. Ranids are characterized by smooth, moist skin, large eardrums, and powerful hind legs for swimming.
Size
One of the largest frogs in North America. SVL typically ranges from 3.5 to 6 inches (9–15 cm), but can reach 8 inches. Weights can exceed 1 lb (0.5 kg). Females are generally larger than males.
Conservation
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are considered a major threat to local biodiversity due to their appetite and spread of chytrid fungus.
Description
The American Bullfrog is the heavyweight champion of the North American frog world. Sitting regally on a lily pad, it maintains a stoic presence until a prey item wanders too close, at which point it strikes with explosive speed.
Key Features
Large size, olive/brown color, lack of dorsolateral ridges on back, and a skin fold that circles only the ear (tympanum).
Physical Description
A large, robust frog with a broad head and powerful limbs. It lacks dorsolateral ridges (folds of skin) on the back; instead, a prominent ridge runs from behind the eye, around the tympanum, and down toward the shoulder. The tympanum (eardrum) is very large and distinct.
Skin Texture & Coloration
Skin is generally smooth but can be slightly granular on the back. Coloration ranges from olive-green to brown, often with dark mottling. The underside is creamy white to yellow. Males often have a bright yellow throat during the breeding season.
Distinguishing Features
The most diagnostic feature is the absence of dorsolateral folds extending down the back. The ridge curving around the large tympanum is key. In males, the tympanum is significantly larger than the eye, while in females, it is roughly equal in size.
Habitat
Highly aquatic; found in permanent bodies of water such as ponds, lakes, marshes, and slow-moving rivers. They prefer areas with aquatic vegetation like water lilies for cover and hunting.
Geographic Range
Native to central and eastern North America. However, it has been widely introduced to the western United States, Europe, Asia, and South America, where it often becomes invasive.
Behavior
Primarily nocturnal but active during the day. They are solitary and territorial. When threatened, they often make a short 'squawk' as they jump into the water to escape. They are aggressive predators.
Diet & Feeding
Vicious generalist predators. They use a sit-and-wait ambush strategy to eat anything they can swallow, including insects, crayfish, fish, lizards, snakes, birds, and even other frogs.
Reproduction
Breeding occurs in late spring and summer. Males congregate in choruses. Females lay up to 20,000 eggs in large floating mats. Amplexus is axillary (under the arms).
Vocalizations
A deep, resonant, two-note bass call often described as 'jug-o-rum' or 'better-go-rum.' The low frequency can carry for over half a mile.
Life Cycle
Eggs hatch in 3-5 days. The tadpole stage is exceptionally long, often lasting 1 to 2 years before metamorphosis into a froglet. Adults can live 7-9 years in the wild.
Conservation Status
IUCN Status: Least Concern. Populations are stable or increasing. In many regions, they are considered a major threat to local biodiversity due to their appetite and spread of chytrid fungus.
Toxicity & Defense
Not toxic to humans. They rely on camouflage, their large size, and rapid escapes into deep water for defense. They may inflate their bodies to appear larger to predators.
Ecological Role
Top predator in many pond ecosystems. In their native range, they balance insect and crustacean populations, but as an invasive species, they can decimate local amphibian and bird populations.
Similar Species
Green Frog (Lithobates clamitans), which possesses prominent dorsolateral ridges extending halfway down the back, and the Pig Frog (Lithobates grylio), which has more pointed toes.
Observation Tips
Best found at night using a flashlight to spot the 'eye shine' reflecting from the water's edge or on lily pads. On warm summer nights, follow the deep 'jug-o-rum' chorus.
Handling & Safety
Safe to handle, though they are slippery and powerful. Always wash hands after contact to avoid salmonella. Handling should be minimized to avoid damaging their protective mucus layer.
Seasonal Activity
Active from early spring through autumn. In colder climates, they hibernate in the mud at the bottom of ponds during the winter months.
Cultural Significance
Famous in American literature through Mark Twain's 'The Celebrated Jumping Frog of Calaveras County.' They are also a traditional food source (frog legs).
Interesting Facts
Bullfrogs are known to stay awake for long periods and may not experience 'sleep' in the same way mammals do. They are also famous for the 'jumping frog' contests in literature and folklore.
Notes
In pond on lily pad