The bullfrog is best known for its loud call that resembles the mooing of a cow. The deep croak of the bullfrog can be heard anywhere from Canada, throughout the United States, down to Mexico, through South America and even over to Europe and Asia. Bullfrogs live in groups called armies or colonies along the edges of lakes, ponds, and swamps.

The largest of the North American frogs, bullfrogs weigh up to 1.5 pounds (750 grams) and their bodies alone measure from 3.5 to 6.0 inches (9–15 cm). Their legs add another 7–10 inches (17–25 cm) to their length. Using these long, powerful legs, bullfrogs can jump an impressive 3-6 feet (0.9-1.8 m).

Bullfrogs are typically green, grayish brown, and yellow with black and brown spots and are marked by their circular eardrums, called tympanum, on either side of their heads. Bullfrogs breathe through their buccal cavities, lungs, and also their skin; a process called cutaneous exchange.

These nocturnal amphibians prey on just about anything they can fit inside their mouths including insects, rodents, fish, snakes, birds, other frogs and in the strangest of cases, bats. They wait quietly and then use their sticky retractable tongue to snatch their prey and pull it into their wide-open mouths, using their arms to stuff in larger catches.

A mature female can lay up to 25,000 eggs at a time. Once the eggs hatch large tadpoles about 6.75 inches (17.2 centimeters) in length emerge and undergo the stages of change: premetamorphosis, prometamorphosis and finally, metamorphosis for up to two years. It is thought that these longer periods of transformation result in bigger, stronger frogs.

Bullfrogs typically live from 7 to 9 years, but can live up to 13 or 14 years in warmer climates. Due to their species being so strong, bullfrogs currently face no danger of extinction.