Forest Preserve District of Cook County, Illinois
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The Bullfrog
Nature Bulletin No. 415-A   April 17, 1971
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

On warm spring nights, in addition to mysterious squeaks, splashes, thumps and rustling noises, we have concerts that go on and on in the ponds and sloughs of our forest preserves -- choruses of peeps, chirps, croaks, rattles and long trills that are the mating songs of the frogs and toads. Not until late May or early June, however, do we hear that deep- throated "jug-o'-rum, jug-o'-rum, jug-o'-rum" which is the call of the male Bullfrog. If he happens to be nearby it sends shivers down your spine and makes you wonder if, when the earth was young and the first queer creatures crawled out on land, they shattered the silence with such rumbling bellows.

With the exception of the Giant Frog of West Africa, the bullfrog is the largest of all the 2000-odd 'species of frogs and toads. It has been known to reach a weight of 7 pounds and a total length, when stretched out, of 18 inches including hind legs 10 inches long. Native throughout most of the United States east of the Rockies, it has been introduced in the Pacific coast states and in Japan.

Early May, in this region, is when the adult bullfrogs come up out of the mud and muck where they have been hibernating since the previous autumn. Later, the males begin the booming bass calls from which they get their name. The females answer less loudly. In addition, they can give a sort of yelping "snurp" as they dive for safety and, when caught, a piercing human-like scream. The bullfrog has a broad Mat head and a dull green or greenish brown head. The ears of the male are about twice the diameter of the female's ears. Its skin is fairly smooth and without any folds running down the sides. The Green Frog, sometimes mistaken for a young bullfrog, has a bright metallic-green head and shoulders with a fold of skin along each side of its body.

About the first of July the female lays 10,000 or more tiny eggs in a large mass of watery jelly that floats in a thin layer at the surface. In a few days the little tadpoles develop until they can wriggle free and are on their own. With their small mouths and rasping lips they suck up ooze and nibble algae or other plants. In these northern states they do not change into frogs until the end of their third summer when they may be 6 inches long and have heads as big as hen's eggs.

During their last few months as tadpoles, the hindlegs grow steadily, the broad fin-like tail is absorbed, the front legs break out through the gill chamber, and they begin to breathe air. They are then little frogs about 2 inches long with broad gaping mouths adapted to catching and swallowing crayfish, snails, water insects, and smaller frogs and toads. As adults they may also devour small turtles, snakes, birds and mice. After another 2 years they are 4 to 5 inches long and begin to breed. They have been known to live 15 years in captivity.

Bullfrogs have a host of enemies. Little tadpoles are preyed upon by water beetles, water bugs and fish. Larger tadpoles and adults are eaten by larger fish, water snakes, herons and other water birds, snapping turtles, raccoons, mink, skunks and owls, but man is their worst enemy. Frog legs have been a delicacy of epicureans since Roman times and today, in America, over 3 million pounds of bullfrog legs -- at 4 or 5 pairs to the pound -- are marketed each year. Schools use a half-million bullfrogs annually in biology courses. As a result, most states have closed seasons and other restrictions on bullfrog hunting.

Try sitting quietly for at least a half-hour near a pond or marsh. It's good medicine, and there's no telling what you may see and hear.

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