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Learn All About Bullfrogs, Our Biggest Frog Friend

The biggest frog in Illinois and all of North America is the American bullfrog. It is a pretty common sight along the water's edge, but it can be hard to get a good look at them because they usually leap into the safety of the water before people — and other potential dangers — get too close.

An American bullfrog. (Photo by Anthony Schalk)

These big frogs are typically between 3 1/2 inches and 6 inches long and can weigh more than a pound. They can live nearly anywhere with a permanent water source nearby, but they prefer warm, shallow waters. They are omnivores, but they mostly eat other animals. They aren't picky. They will eat any animal they can catch and swallow.

Frogs and other amphibians are typically sensitive to changes in their environment because they have porous skin. However, bullfrogs are less susceptible to these changes and better tolerate human modifications to their habitat than most amphibians.

Their jumping ability is no joke

If you've ever walked along the edge of a lake or a pond, you've probably seen frogs and toads leaping into the water to escape danger. How far bullfrogs can leap is pretty impressive. These frogs can jump 6 feet without much difficulty. Longer jumps aren't unheard of either. Most of their jumps aren't quite so spectacular, however. On average, their jumps measure about 3 feet.


Words to know

Anatomical: Related to bodily structure.

Modification: The act of changing something.

Nocturnal: Occurring at night.

Porous: Having small holes through which liquid or air can pass.

Tolerate: Being able to exist in spite of environmental changes.


Bullfrogs are among the best jumping frogs in the world, partly due to their large size compared to most frogs. In some places, bullfrogs are used for frog racing and frog-leaping contests. One of the most famous frog-jumping contests in the world is the Calaveras County Jumping Frog Jubilee, held each year at the Calaveras County Fair in Angels Camp, California. In the Jumping Frog Jubilee, each frog and its jockey are allowed three jumps. The world record at the event was set back in 1986, when Rosie the Riveter leaped a total of 21 feet, 5 3/4 inches, or an average of 7.16 feet per jump.

They are very loud

As a kid, you probably learned that frogs ribbit, but bullfrogs got their common name because their call sounds like a mooing cow or bull. It's probably unlikely you would confuse a cow's moo with a bullfrog's call, though. A more appropriate description of what a bullfrog sounds like is the call "jug-o-rum" or "br-wum."

An American bullfrog. (Photo by Glenn P. Knoblock)

No matter what you think when you hear them calling, you can hear them up to a half-mile and sometimes even farther from where they are. That means a chorus of bullfrogs may be part of your nocturnal soundtrack even if you don't live that close to water.

Only male bullfrogs croak, and they do it for the same reason many other male animals make noise: to establish their territory and attract a mate. To croak, male bullfrogs breathe air in, then close their nostrils. After inhaling, they move the air backward and forward between their lungs and their vocal sac. This is what creates the sound we are so familiar with.

It probably takes longer than you think to transform into a frog

You probably know that frogs are tadpoles before they transform into adult frogs. And you might even know that before they are tadpoles, frogs start as eggs. But did you know it can take up to three years for those eggs to become mature frogs?

The first part of their life cycle happens quickly. The tadpoles hatch from jelly-like eggs after about four days. The transformation from tadpole to frog can take years, however. Over the course of a year or two, the tadpoles will grow to be 4 inches to 6 inches long before finally transforming into a frog.

The longer it takes for a tadpole to fully transform into an adult frog, the bigger the frog will be. Through the full course of their life cycle, bullfrogs can live more than 10 years in the wild. Their average lifespan is five to six years.

The females can lay thousands of eggs

A single female bullfrog can lay as many as 20,000 eggs at once. The eggs typically float in a thin sheet at the water's surface.

The large number of eggs is necessary to help ensure some of them hatch and some of the resulting tadpoles survive into adulthood. Frog eggs are vulnerable for many reasons. First, they are a welcome food source for many aquatic animals. The eggs also must remain wet or they will shrivel up and the tadpoles won't hatch. Plus, frog eggs are fertilized after they are laid, so some may never be fertilized and have a chance of hatching.

The hatch rate for bullfrog eggs varies based on these factors, but a rough estimate is that about 1 in 50 eggs hatches into a tadpole. So of those 20,000 eggs, only about 400 will grow to be tadpoles — only about a 2% success rate. But those 400 tadpoles won't all necessarily become frogs either. Just like the eggs, tadpoles are also eaten by many other animals as well.

It's easy to tell males and females apart

It's not always so easy to tell male animals from their female counterparts, but in bullfrogs it's actually not that difficult based on two anatomical features. The easiest way to distinguish male and female bullfrogs is their tympanum, which is an external eardrum. The tympanum is located right behind a frog's eye, and using its eye for size comparison is a good way to tell if you are seeing a male or female bullfrog. In females, the tympanum will be about the same size as the frog’s eye. In male bullfrogs, the tympanum will be much larger than a frog’s eye.

An American bullfrog. (Photo by Anthony Schalk)

During breeding season, their throats are also a distinguishing characteristic. Males have yellow throats during breeding season, and females have white throats. And of course, if you hear a bullfrog calling out its famous "jug-o-rum," you'll know it's a male because only male bullfrogs call. In addition, as with most frog species, males are smaller than females, although this may not be easy to distinguish just by looking at a frog.


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