Common Bullfrog

Rana catesbiana Shaw

Colour.—Green or greenish brown, of light or dark shade. The back and sides may be plain in colour or may be spotted with dark. The spots, when present, may be distinct or connected. Arms and legs spotted or barred with dark. Underparts white, distinctly or obscurely spotted and mottled with dark. The throat of the male may be yellow. The iris is either golden or reddish bronze.

Measurements.—Size large, both male and female often reaching a length of 7 to 8 inches. The leg to the heel is not as long as the combined lengths of head and body. The femur is about equal to the tibia.

Structure.—The head is broad and flat. The body is stout and flat. Ear of male much larger than the eye the ear of the female is about the size of the eye. The lateral folds are lacking. A strong fold of skin extends from behind the eye to the arm, curving around the ear. Toes broadly webbed; no joints free, except the last of the fourth toe.

Range.—Rana catesbiana Shaw is found in North America, east of the Rocky Mountains (including Florida and Texas).

Bullfrogs are late in coming permanently from their hibernation. (Solitary individuals may remain active throughout the winter, in spring houses or large springs, in the vicinity of Philadelphia.) It may not be until late May or early June that we hear their deep bass voices from the ponds, or that we see their gigantic green bodies perched on partially immersed logs or floating among water-weeds at the surface. They prefer large ponds or lakes, where they can find deep water as well as shallow, screened from the shore by low willows, alders or other water-loving plants. They like such places, also, because of the sheltering growths of pickerel-weed, arrowhead, and water-lilies. These make good hiding-places, and about the roots and stems and under the leaves are to be found crayfishes, water-beetles and bugs, snails and shrimps, the larvae of dragon-flies and May-flies, and, in fact, all sorts of delicacies for a water frog's menu. For the Bullfrog differs from the Leopard and Pickerel frogs, in that it does not hunt in any place except the body of water which makes its home. We shall not find Bullfrogs when we go for country walks across meadows and through orchards, even though the meadows and orchards may be near ponds or lakes. We are more likely to see them if we go rowing on river or pond. The Bullfrog is more thoroughly aquatic than any of the other frogs of northeastern North America. However, if we happen to be walking across country, or even along a country road during a long-continued heavy rain, we may overtake a large Bullfrog who seems to be making the same journey. Whether the continued wet weather has tempted him to go hunting beyond his usual bounds, or whether he is migrating from pond to pond, it would be difficult to say. He proceeds by successive leaps, about three feet each in length. He can cover a distance of five or six feet without difficulty, notwithstanding his large, heavy body. A wet Bullfrog leaping across a dry surface leaves curious tracks, interesting in that they show how large a part of the under portion of the body and thighs strikes the ground forcibly after each leap, and how the frog "toes in" with its front feet.

The Bullfrog is our largest frog. He may measure six or seven inches from the tip of the muzzle to the posterior end of the body. A young frog of this species, which had been raised in the laboratory, measured four inches in length on his first birthday. However, size is not a good criterion by which to judge the age of a Bullfrog, or even its identity. The variation in this particular is marvellous. A frog one year old may be no more than two inches long. Much depends on the size attained by the tadpole before the transformation, and of course much also depends on the food and other conditions of the environment, and the ability of the individual frog to cope with these conditions.

The Bullfrog is very easily distinguished from other frogs, however, whatever may be its size. The head is broad and flat. (The head of the young Bullfrog is relatively less broad than that of the adult.) The ear is much larger than the eye. There are no lateral folds. There is a short fold of skin extending backward from the eye, over the ear, and down to the shoulder. The hind feet are fully webbed.