Photo by Jeff Hall
Scientific Name: Rana catesbeiana
Classification: Nongame species
Juvenile Bullfrog (Photo by Jeff Hall)
A booming "roo-roo-room" or "jug-or-rum." Also, a shrieking "alarm call" as they leap into the water. Males defending territories against other males may utter an abrupt, spitting "phfoot!" as an "aggression call."
The largest frog species in North America, the bullfrog usually grows 6 to 8 inches long and weighs 2 to 3 pounds. Males typically outweigh females, but both sexes look much the same with a heavy build, big head, bright eyes and strong limbs. Their skin is smooth and olive green with dark, mottled patterns on their sides and bellies. A bullfrog’s color may vary with its habitat. Bullfrogs at the coast, for instance, will be darker green and have darker markings than those in the mountains. It takes a close look to determine the sex of a bullfrog. Males sport a yellow throat during breeding season that they protrude when making their lowpitched calls. A female’s throat looks cream-colored.
Bullfrogs do not sing in chorus, as many believe, but several males may croak their familiar call at the same time across a pond, especially after a heavy rain. Most often they sing solo, anytime day or night, from late spring into the summer. Their call resembles the sound of a distant bull, giving them their name. The distinct “jug o’ rum” or “kneedeep” call can be heard for more than a quarter mile. Males use the low-pitched croak to attract a mate, call to another male or stake out a territory. The female’s call sounds like a high-pitched scream. Learn more by reading the American bullfrog species profile.
The bullfrog is classified as a nongame species with no open season. It is unlawful for any person to take, or have in possession, any nongame mammal or bird unless that person has a collection license or is collecting fewer than 5 reptiles or fewer than 25 amphibians that are not endangered, threatened, or special concerned species.
There are no reported human-interaction problems with this species.
Frogs and toads can be monitored fairly easily in a variety of ways. One way is through frog call monitoring. The North Carolina Calling Amphibian Survey Program attempts to do just that by corralling data collected by volunteers across the state that monitors specific frog call routes. Each species of frog and toad has a unique call that is distinguishable from others. Some are more difficult for humans to separate than others, but the frogs know who’s who! Learn your frog calls, and you too can distinguish who’s calling in the ponds. Another way to monitor frogs and toads is by looking for egg masses deposited in wetlands and/or by looking for tadpoles in those same wetlands. Different frogs breed at different times of the year, so when to look for eggs is dependent on the species of interest. Eggs typically hatch within a couple weeks of being deposited, so there is a fairly short window for detection. Frog eggs can sometimes be identified to family, but are somewhat tricky to identify to species level. Tadpole identification can be similarly tricky, so learning and listening to frog calls is definitely the easiest method for determining what frogs and toads are using a wetland. Tadpoles are a little easier to monitor, as most species have tadpoles present in wetlands for longer periods of time. This is, again, variable by species. Most species have tadpole stages that last at least several months, but the range in timing for different species is everything from a couple of weeks to several years. The smaller frog and toad species tend to have shorter tadpole cycles, while the larger frogs and toads tend to have longer times to metamorphosis.
Bullfrog Species Profile (PDF)
Wildlife Diversity Program Quarterly Reports