American Bullfrog (Amphibians and Reptiles of Floracliff Nature Sanctuary )

American Bullfrog

Lithobates catesbeianus

Adult characteristics ³

The American Bullfrog is a large species, growing up to 200mm (8in) at maturity. Dorsal color is green to dark olive, ventral color is cream to yellow. There is a noticeable tympanum, especially in males. Dorso-lateral ridges are present and hind feet are fully webbed.

Behavior ⁴

This is a wary and solitary species that prefers large ponds, lakes, and still portions of streams. Males of this species defend territories typically within vegetated areas of ponds. Defending behaviors include encounter calls, postural displays, chasing the intruder, and combat. Size and age strongly determine territory success. This is a voracious predator feeding on insects, crayfish, small mammals, snakes and other frogs. Experiments have demonstrated that this species has the ability to orient to stellar patterns or the moon .

Description ⁵

Size: 3 – 8 inches (the largest frog in North America)

Color: Green to brown or yellow

Have smooth skin with a ridges that runs along both sides of the back beginning behind the eye, running over the ear drum and ending at the base of the front legs.

Habitat: Ponds, lakes, slow moving streams with vegetation. (Must be large enough to avoid crowding). Usually found on the bank at water’s edge. When frightened, the bullfrog is likely to flee into nearby vegetation. Large specimens have been known to catch and swallow small birds and young snakes.

Diagnosis ⁶

The dorsal (upper) surface of the bullfrog has an olive-green basal color, either plain or with a mottling and banding of grayish brown. The ventral (under) surface is off-white blotched with yellow or gray. Often, a marked contrast in color is seen between the green upper lip and the pale lower lip.[1] The teeth are tiny and are useful only in grasping.[2] The eyes are prominent with brown irises and horizontal, almond-shaped pupils. The tympani (eardrums) are easily seen just behind the eyes and the dorsolateral folds of skin end close to them. The limbs are blotched or banded with gray. The fore legs are short and sturdy and the hind legs long. The front toes are not webbed, but the back toes have webbing between the digits with the exception of the fourth toe, which is unwebbed.[1]

Bullfrogs are sexually dimorphic, with males being smaller than females and having yellow throats. Males have tympani larger than their eyes, whereas the tympani in females are about the same size as the eyes.[1] Bullfrogs measure about 3.6 to 6 in (9 to 15 cm) from snout to vent. They grow fast in the first eight months of life, typically increasing in weight from 5 to 175 g (0.18 to 6.17 oz),[3] and large, mature individuals can weigh up to 500 g (1.1 lb).[4] In some cases bullfrogs have been recorded as attaining 800 g (1.8 lb) and measuring up to 8 in (20 cm) in length.[3][5]

Egg characteristics ³

American Bullfrog eggs are laid in large sheets on pond water surface and hatch in less than one week.

Habitat ⁷

It inhabits large, permanent water bodies, such as swamps. This species requires medium to large permanent bodies of water to meet their one to two year early developmental period. Clutches of eggs are laid in still shallow water. Bullfrogs are prized for the meat of their hind legs, and the demand for frog legs has even led to the deliberate introduction of this species to waters both in the U.S. and abroad. It is usually found in aquatic vegetation or snags in which it can hide.

https://www.virginiaherpetologicalsociety.com/amphibians/frogsandtoads/american-bullfrog/american_bullfrog.php
https://www.nationalgeographic.com/animals/amphibians/a/american-bullfrog/
https://www.aqua.org/Experience/Animal-Index/american-bullfrog

Physical Description ⁷

This frog has an olive green back and sides blotched with brownish markings and a whitish belly spotted with yellow or grey. The upper lip is often bright green and males have yellow throats. The average length is 3.5 to 6 inches. Bullfrogs are typically green or gray-brown with brown spots and have easily identifiable circular eardrums, or tympanum, on either side of their heads. Their hind feet are fully webbed. Life expectancy for female frogs in a study in Michigan was found to be 4 years. The longevity record for a specimen in captivity was 16 years. Larval survivorship is typically less than 18%

Reproduction ⁷

Females lay thousands of eggs (as many as 20,000) during the summer breeding season. In the southern part of a bullfrog’s range, metamorphosis can take as few as 79 days. While in the colder, northern part of their range it can take two to three years. This species breeds from the late spring to early fall. Mating success is influenced by the quality of the territory. The male breeding call is a deep, full series of notes. Females lay one or two clutches per season. Clutches are laid in a film on the water surface. Eggs hatch in approximately 5 days. Tadpoles can be very large, 125-150 mm. This species typically reaches sexual maturity one year after metamorphosis.. In mountain localities, transformation may take 2 years.

Sound ⁵

Voice: Deep-pitched “jug o'rum” resembling the bellow of a bull.

Sound produced by a single internal vocal sac that inflates to form a bulge under the chin. Call can be heard for more than a quarter mile.

Tadpole characteristics ³

American Bullfrog tadpoles are large (4cm) and speckled with a well defined lateral line. Tadpoles overwinter before metamorphosis occurs.

Sources and Credits

More Info

iNat Map

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