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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. There is often a marked contrast in color 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 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 forelegs are short and sturdy and the hind legs long. The hands are not webbed, but the feet have webbing between the digits with the exception of the fourth toe which is unwebbed. 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. 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), and large mature individuals can weigh up to 500 g (1.1 lb). In some cases bullfrogs have been recorded as attaining 800 g (1.8 lb) and measuring up to 8 in (20 cm) in length.
The bullfrog is native to eastern North America. Its natural range extends from the Atlantic Coast to as far west as Oklahoma and Kansas. It is not found on offshore islands near Cape Cod and is largely absent from Florida, Texas, Colorado, Nebraska, South Dakota, and Minnesota. It has been introduced into Nantucket island, Arizona, Utah, other parts of Colorado and Nebraska, Nevada, California, Oregon, Washington, and Hawaii. In these states, it is considered to be an invasive species and there is concern that it may outcompete native species of amphibians and upset the ecological balance. It is very common in California, where it is believed to pose a threat to the California red-legged frog and is considered to be a factor in the decline of that vulnerable species.
Spotted on Sep 5, 2014
Submitted on Sep 5, 2014