Wisconsin Sea Grant Frogs: Field Guide
Call: Males give a distinctive, deep "bur-rum"
Size: 9-20 cm in length (3.5-8 inches)
Green, olive, or brown with brownish spots on back and dark bands on upper
legs; belly is white or cream-colored. Males have yellow throats, females
Any still, permanent body of water; bullfrogs are found throughout the
Great Lakes region except along northern Lake Superior. They are common
in golf course ponds in the upper Midwest.
Green Frogs have distinct dorsolateral
folds extending at least partway down the back, and their adult size is
smaller. The smaller, darker Mink Frog of the far north may lack dorsolateral
folds but has rounded spots or lengthwise blotches on the upper surface
of the hind legs and a musky, mink-like odor when handled.
Breeding: Mid-May into July
Did you know?
Bullfrogs are the largest frog species in North America,
with adults growing up to eight inches long.
The bullfrog tadpole is big too - up to six inches long,
including its tail! These tadpoles can take two years to mature into frogs.
In fact, large bullfrog tadpoles sometimes can be seen through the ice
in frozen ponds in winter.
Male bullfrogs are territorial and defend their home
turf by calling out to warn intruders. If that doesn't work, a shoving
or wrestling match may follow!
From May to July the male bullfrog's deep "bur-rum" call attracts
females, who lay eggs in large, jelly-like masses that can measure a yard
across. Smaller males that cannot compete with large males for territories
have evolved a trick. They hide out near the large calling male and intercept
females attracted to the big male. By this strategy, the small males are
able to occasionally mate and pass on their genes.
Bullfrogs are famous for their big appetites. As tadpoles,
they eat mostly algae, but
adults eat just about anything they can catch and cram in their mouths,
including other frogs. Some of the more unusual items on their menu include
insects, garter snakes and even ducklings.
Bullfrogs themselves are eaten by birds, turtles, raccoons and snakes.
Humans also have developed a taste for bullfrogs -- you might even see
bullfrog legs on a restaurant menu.
copyright 2001 University
of Wisconsin Sea Grant Institute