The Bullfrog, Rana catesbeiana Shaw, in the Lower Colorado River, Arizona-California

The bullfrog, Rana catesbeiana, achieved an average adult density of 9.1 per linear kilometer in the lower Colorado River between Laguna and Morelos dams, Arizona-California, during the summer of 1981. Significantly greater numbers of frogs were observed in transects with 50% or more bank cover provided by reeds (Phragmites australis and Arundo donax), and/or less than 50% open bank. Food habit analyses added new records of muskrat (Ondatra zibethicus) and rattlesnake (Crotalus atrox), to prey items of the bullfrog. We compare bullfrog breeding behavior in riverine and lentic populations.