Vocalization, Aggressive Behavior, and Territoriality in the Bullfrog, Rana catesbeiana

The relationships among vocalization, aggressive behavior, and territoriality in Rana catesbeiana were investigated using a playback technique and a ceramic model of a bullfrog. When a tape recording of a mating call was played to a territorial male, he usually attacked the model situated in shallow water by the loudspeaker. These attacks were similar to encounters between fighting males observed under natural conditions. Males responding to playback invariably emitted a curt vocalization, termed a bonk. Experimental evidence and observations strongly suggest that this signal is associated with the establishment and maintenance of territory. By noting the response of the frogs to playback at various points around a pond, it was possible to estimate the dimensions of each male's territory. The three most responsive frogs defended from 9 to 25 m of shoreline, but the territories fluctuated somewhat through a summer