In a 1913 study, it was found that bullfrogs will eat any animal it can overpower and stuff down its throat. Bullfrog stomachs have been found to have rodents, baby muskrats, small turtles, snakes, frogs (including bullfrogs), birds, and a bat, as well as the many invertebrates, such as insects. These studies show the bullfrog's diet is unique among North American "Rana". Bullfrogs are also known to eat ducklings and tadpoles. Bullfrogs have teeth on the top of their mouths. Their tongues are capable of flipping their food into their mouths. Bullfrogs will eat at night.