NISAW: Bullfrog

Today, for National Invasive Species Awareness Week,  we are going to meet the American Bullfrog (Lithobates catesbeianus AKA Rana Catesbeiana).

American Bullfrog, photo taken by Carl D. Howe, retrieved from wikimedia commons

American Bullfrogs are native to the Eastern United states and are thought to have spread through trout stockings and the aquarium trade.  Bullfrogs tend to be large frogs, their bodies can be anywhere from between 3 to 8 inches long and they have long powerful legs that can be up to 10 inches in length. They are great jumpers, with their long powerful legs, they can jump up to around 6 feet in distance.  They are usually green to greenish-brown in color.Their eyes are golden brown and they have a broad, flat head. They do not have dorsolateral ridges--ridges or stripes that run down each side of the back.  They do have large and conspicuous tympanic membranes, ear drums, which look like big circles on the sides of their head right behind their eyes.   Their call is a deep pitched "jug-o-rum" or "Br-wum" bellow.  You can hear this call right before they jump in the water, you'll often hear the call followed by a splat of water. 

The American bullfrog has been introduced in many areas around world. They have successfully spread through much of the Western United States, including the Basin and Range.  Their large size, reproductive capabilities and generalized eating habits--they will pretty much eat anything that can fit into their mouths, birds, rats, snakes, lizards, turtles, fish, other frogs, and even each other--have made bullfrogs extremely successful invaders.   In their native home, their large size and aggressive behavior make them important competitors and predators.  In their introduced range, however, bullfrogs are a serious threat to sensitive aquatic species such as native amphibians, reptiles, and fish .

Sources:
U.S. Forest Service, "Rana Catesbeinana entry,"accessed 3-1-2012, see entry here.