American Bullfrog
Rana catesbeiana

Description: American Bullfrogs are brown or green in color. There may be dark blotches on the back and legs. The throat and belly are white or yellow with gray spots. The hind feet are webbed. Males can be distinguished from females by the size of their tympanum (eardrum). A male bullfrog's tympanum is much larger than its eye, while a female bullfrog's tympanum is about the same size as its eye.

Size: The American Bullfrog can weigh as much as one pound and measures an average of 4-6 inches long.

Adaptations:

• American Bullfrog eggs and tadpoles have an unpleasant taste. This protects them from being eaten by predators.

• The bullfrog's incredibly strong legs give it the ability to jump long distances. A bullfrog can jump up to 2 feet, which is several times its body length!

• The brownish-green color of this frog helps it to blend in with its surroundings and provides excellent camouflage.

• Frogs and other amphibians have a slimy covering on their skin. This helps to keep their bodies moist.

Diet: Adult bullfrogs are carnivores that consume a variety of prey including worms, insects, crustaceans, and even other frogs and their eggs. Tadpoles eat aquatic plants. At Cosley Zoo, the bullfrogs are fed crickets, earthworms, small mice, and a vitamin supplement.

Reproduction: In this area, American Bullfrogs breed once a year between May and July. After the female lays the eggs, the male discharges sperm over the eggs to fertilize them. Female bullfrogs may lay up to 20,000 eggs at a time! Tadpoles emerge 4 days after the eggs are fertilized, and may take up to 2 years to transform into adults.

Shelter and space needs: Bullfrogs prefer areas with warm, still, shallow water and are found near water sources such as lakes, ponds, or bogs.

Life expectancy: In the wild, bullfrogs live 7-9 years. In captivity, they can live up to 16 years.

Importance to man: Frogs and other amphibians are known as “environmental indicators” because they are extremely sensitive to changes in the environment. A high mortality rate or an increase in birth defects can be a sign that an area is becoming polluted. American Bullfrogs are important predators of many insect pests. They are also prey for many animals including snapping turtles, herons, skunks, and raccoons.

Fun Facts:

• The American Bullfrog is the largest frog in Illinois!

• One interesting behavior of frogs is sloughing, or shedding the skin. When a frog is ready to shed, it will open its mouth very wide and stretch its body out, loosening the skin. The frog will then use its legs to pull the skin over its head, shove the skin into its mouth, and eat it!

• Did you know that a frog's eyes help it to swallow? When frogs swallow, they close their eyes, which then sink down into their heads and help to push the food down their throats.

• Frogs can breathe through their skin! They have lungs, like we do, but they can also absorb oxygen through their moist skin. This is especially useful when the frog is underwater. Because their skin is much more absorbent than ours, it is also more fragile. It is not a good idea to pick up or handle frogs because by doing so, we are likely to damage their sensitive skin.

• A group of frogs is called an army.