Rana catesbeiana

The American bullfrog (Lithobates catesbeianus), often simply known as the bullfrog in Canada and the United States, is a large true frog native to eastern North America. The bullfrog gets its name from the sound the male makes during the breeding season, which sounds similar to a bull bellowing. The bullfrog is large and is commonly eaten throughout its range, especially in the southern United States where they are plentiful.

Other than for food, bullfrogs are also used for dissection in science classes. Albino bullfrogs are sometimes kept as pets, and bullfrog tadpoles are often sold at pond or fish stores.

DESCRIPTION

• The dorsal (upper) surface of the bullfrog has an olive-green basal color, either plain or with 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.

• The teeth are tiny and are useful only in grasping.

• The eyes are prominent with brown irises and horizontal, almond-shaped pupils.

• The tympana (eardrums) are easily seen just behind the eyes and the dorsolateral folds of skin enclose 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.

• Bullfrogs are sexually dimorphic, with males being bigger than females and having yellow throats.

• Males have tympana larger than their eyes, whereas the tympana in females are about the same size as the eyes.

• Bullfrogs measure about 3.6 to 6 in (9 to 15 cm) in snout–to–vent length. They grow fast in the first eight months of life, typically increasing in weight from 5 to 175 g and large, mature individuals can weigh up to 500 g.

REPRODUCTION

• After selecting a male, the female deposits eggs in his territory.

• During the mating grasp, or amplexus, the male rides on top of the female, grasping her just behind her fore limbs. The female chooses a site in shallow water among vegetation, and lays a batch of up to 20,000 eggs, and the male simultaneously releases sperm, resulting in external fertilization.

• The eggs form a thin, floating sheet which may cover an area of 0.5 to 1.0 m2 (5.4 to 10.8 sq ft).

• The embryos develop best at water temperatures between 24 and 30 °C and hatch in three to five days. If the water temperature rises above 32 °C, developmental abnormalities occur, and if it falls below 15 °C , normal development ceases.

• Newly hatched tadpoles show a preference for living in shallow water on fine gravel bottoms. This may reflect a lesser number of predators in these locations.

• As they grow, they tend to move into deeper water. The tadpoles initially have three pairs of external gills and several rows of labial teeth. They pump water through their gills by movements of the floor of their mouths, trapping bacteria, single-celled algae, protozoans, pollen grains, and other small particles on mucus in a filtration organ in their pharynges.

• As they grow, they begin to ingest larger particles and use their teeth for rasping. They have downward-facing mouths, deep bodies, and tails with broad dorsal and ventral fins.

• Time to metamorphosis ranges from a few months in the southern part of the range to 3 years in the north, where the colder water slows development.

• Maximum lifespan in the wild is estimated to be 8 to 10 years, but one frog lived for almost 16 years in captivity.

HABITAT

It typically inhabits large permanent water bodies such as swamps, ponds, and lakes. Bullfrogs can also be found in manmade habitats such as pools, koi ponds, canals, ditches and culverts.