Bullfrog (Rana catesbeiana)
In our area, bullfrogs have spread widely along the vicinity of the lower San Pedro River, but mostly in artificial ponds. They have only recently been seen breeding or in many numbers along the River itself. They are present near Bingham Cienega and Redfield Canyon, and well to the south around Benson and St. David (an area strongly dominated by non-native fish, frogs, and crayfish). But so far Hot Springs Canyon and Paige Creek remain the province of the Lowland Leopard Frog (Rana yavapaiensis), a native species which has been largely eliminated where exotic aquatic species are strongly present. (See Philip Rosen and Cecil Schwalbe, "Widespread effects of introduced species on reptiles and amphibians in the Sonoran Desert Region", in Tellman op.cit., especially pp. 230-38 and figure 12.6.) Thanks to the accompanying photograph (adapted from Collins, see citation on main Invasive Animals page), our Associates should be able to distinguish these invaders from our own Sonoran Desert Toads.
For a PDF with further information on Bullfrogs (and Crayfish), see this link: AZGFD Arizona Backyard Ponds.