The American Bullfrog (Rana catesbeiana) is the largest frog found in Arizona, but it is not native here. American Bullfrogs were introduced to Arizona from eastern North America. Because they remain in the aquatic tadpole stage for one to three years, these non-native frogs are only found in areas of permanent fresh water. American Bullfrogs are very common in the Sweetwater Wetlands here in Tucson.
Male and female American Bullfrogs can be told apart by the size of the tympanum (the circular external ear located behind the eye). The tympanum of female American Bullfrogs is the same size as the eye or smaller, while the tympanum of the males is much larger than the eye.
Male American Bullfrogs are known for their extraordinarily loud, deep, mooing calls that can be heard over great distances. The males are very territorial and will physically defend sections of the shoreline from other males.
American Bullfrogs are voracious predators and will capture and eat any creature that will fit into their gaping mouths, including smaller individuals of their own species. In areas where they have been introduced, American Bullfrogs prey on native frog species and may actually be driving some of them to extinction. American Bullfrogs are such adaptable predators that they have even been observed capturing and eating low-flying bats.