By Dr. Becker
April is National Frog Month, and to celebrate, we’re featuring a species of frog named Rana [Lithobates] heckscheri, better known as the river frog.
River frogs, or Rana L. heckscheri, can be found only in the US, and are especially prevalent in the southeastern states. They are also frequently referred to as Wright’s bullfrog or river-swamp frog.
River frogs are nocturnal, and large as frogs go. They resemble the American bullfrog and the pig frog, and grow to 3 to 5 inches in length. Their skin is rough and heavily wrinkled, and the color can be yellow-green, dark brown, blackish-green or deep green.
River frogs live by rivers, creeks, lakes, and wetlands because they require a constant water source to thrive and breed.
6 Cool Facts About River Frogs
- River frogs are approachable. They tend to rest where they can be plainly seen by passersby. And while most frogs make a quick exit when a human approaches or tries to handle them, river frogs have an entirely different reaction to human interaction – they play dead. They make their bodies look limp and lifeless.
- They’re stinky. Even though river frogs are more approachable than other frogs, you may want to keep your distance. It seems that in addition to playing dead, river frogs also emit a foul odor as a form of self-defense. In fact, their nasty smell and/or secretions on their skin have been known to make their snake predators gag and retch after eating them.
- Male river frogs sound a bit like Barry White. Male river frogs have a distinctive vocal tone that is deep and booming. (It actually sounds similar to a snore, but don’t tell Barry.) The purpose of the call is to attract females for mating, and the best time to hear it is between April and July. River frogs are also known to snarl and grunt when they’re feeling territorial.
- They have big babies. Like their parents, river frog tadpoles are on the large side and can be up to almost 4 inches long. The youngsters often school together, which is rare for frogs, and the schools can contain several hundred tadpoles. The tadpole stage is about 2 years, at the end of which the juveniles transform at a much shorter 1 to 2 inches in length.
- River frogs have unique physical features. For example, their lips are conspicuously dotted with light spots. They also usually have a pale girdle that outlines the groin. They have no dorsolateral folds or ridges. And tadpoles have red eyes and dark edges on their tail fins.
- Eggs are laid in a floating layer. This floating layer resembles a film on the surface of the water and contains several thousand eggs that hatch after about 3 days. The tadpoles stay in shallow water during the day, and move into deeper water at night. The large number of young frogs compared to a relatively small number of adults indicates there is a high mortality rate for tadpoles and juveniles.