THE ROBINSON LIBRARY
|The Robinson Library >> Science >> Zoology >> Reptiles and Amphibians >> Order Anura|
The largest true frog in North America averages 3½ to 6 inches in length, not counting its legs, which average 7 to 10 inches in length. Like other true frogs it has smooth skin, but some individuals may have small tubercules on the skin surface. Bullfrogs come in a range of colors from greenish to black, with the upper parts generally darker than the underparts. Individual bullfrog color will vary depending on temperature and light conditions, with the bullfrog becoming lighter in the absence of light and darker as the air temperature goes down. Some individual bullfrogs are also marked with bars on the feet and sides, with such markings more common on females than males. The hind feet are fully webbed.
Male and female bullfrogs can be distinguished by the size of the eardrums, which are significantly larger on males than females. Male bullfrogs also tend to develop a bright yellow throat during the breeding season.
Distribution and Habitat
The bullfrog's native range extends over much of the United States east of the Rocky Mountains into southern Canada and along the U.S.-Mexico border., but it has been introduced (both accidentally and intentionally) into the western United States, Mexico, Central and South America, southern Europe, and Asia. Throughout its range it is never found away from some source of permanent water, which can be a pond, drainage area, swamp, river or stream, or even artificial impoundments.
One of the most voracious frogs known, the bullfrog will feed on anything it can overpower and fit into its mouth. While insects, earthworms and spiders form a major part of the diet, bullfrogs are also known to go after crayfish and other arthropods, as well as snakes, rodents, and even birds.
The bullfrog is an ambush predator, waiting for something to come along and then using its lightning-fast tongue to ensnare its prey and bring it toward the mouth. Larger prey may be taken into water and allowed to drown, while smaller prey is often simply crammed into the mouth using the front feet. Although bullfrogs do have teeth, the teeth only serve to keep the prey from escaping the mouth while being swallowed.
The breeding season runs from May to July in the north, February to October in the south, and it is during this time that male bullfrogs give their familiar call, which can be heard up to 1/2 mile away.
Mating consists of the female depositing about 20,000 eggs in water as the male deposits his sperm. It takes about four days for the eggs to hatch into tadpoles, and up to two years for the tadpoles to develop into adult frogs; colder temperatures lead to longer development times, while warmer temperatures allow for faster development. Tadpoles feed on algae, decaying vegetation, and small pond animals.
Bullfrogs have an aveage lifespan of 8-10 years in the wild.
Habits and Behaviors
Bullfrogs are active both day and night, but most movement along water courses takes place at night and overland excursions are limited to rainy nights.
Bullfrogs will hibernate under logs or in burrows during cold weather, with the length and extent of hibernation dependent on climate. Bullfrogs in the north may spend up to six months in full hibernation, while those in more temperate regions may not hibernate at all. Bullfrog tadpoles never hibernate, as they can simply go into deeper water to avoid icy conditions.
Library >> Science >> Zoology >> Reptiles and
Amphibians >> Order Anura
This page was last updated on September 28, 2017.