River Frog

Scientific Name: Lithobates heckscheri
Classification: Nongame species
Range: State Listed as Endangered

Overview

This very rare species is North Carolina’s second largest frog, surpassed only by the bullfrog. The river frog closely resembles the bullfrog but is usually brown or olive with no bright green coloration. Its belly is predominantly gray or blackish, mottled with whitish. It has indistinct whitish spots as well as dark mottling on the upper and lower lips and usually a pale band around the groin. Its skin is usually slightly rougher than that of the bullfrog. Like the bullfrog, it does not have ridges running along its sides. Juveniles usually have a dark reddish iris, which turns brown or golden as the frog matures.

River frogs are known from only a few historic localities along the Lumber and Cape Fear River systems in the southeastern Coastal Plain. River frogs are closely associated with blackwater river habitats, breeding in oxbow lakes, ponds, borrow pits, swamps or other permanent waters along such rivers. Eggs are deposited as a surface film. The river frog’s huge tadpoles are unmistakable and are more easily identified than the adult frogs. Rivaled in size only by those of the bullfrog, they may reach 6 inches in length and are easily identified by three dark stripes running the length of the tail. The tadpoles usually travel in large schools and take a year or more to transform.

River frogs apparently produce skin secretions that are toxic or distasteful to some predators. They are less wary and more easily captured than most other frogs and often go limp when handled. As of this writing, river frogs have not been reported from the state since 1975; they are thought to be extinct in North Carolina.

Call:

Neither eggs nor calling adults have been reported in North Carolina, but in other states, river frogs breed from April to August. Their call is a loud roar or snore, which has been compared to the sound of a distant chainsaw, a lawnmower or a train.

Regulations

The River Frog is classified as a nongame species with no open season. It is state-listed as an endangered species and cannot be collected or taken except under a special permit issued by the Wildlife Commission’s Executive Director. More information is available in the Regulations Digest.

Management

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.

Related Links, Calls & Photos

Wildlife Diversity Program Quarterly Reports

River Frog information on the Amphibians and Reptiles of North Carolina website.

Have a Wildlife Problem?

There are no reported problems with this species.