Inability of mate and species recognition by male Asian toads, Bufo gargarizans

In recent years, we frequently observed missmatched pairs between male Asian toads, Bufo gargarizans, and bullfrogs, Rana catesbeiana, at the toad breeding ponds, where scramble competition for mating occurred among the male toads. Thus, we performed two-choice experiments to investigate recognition ability of mates and species in male toads. The test males did not discriminate sexes, but the clasped stimulus males immediately produced release calls and stopped it while the clasped stimulus female did not. In addition, the test male toads did not discriminate reproductive state of females and even species. However, male toads chose larger individuals. The present results indicate that the main reason of missmatched amplexus by the male toads is due to 1) the lack of recognition cues of conspecifics, 2) the lack of communication tools like release calls, and 3) the larger size of bullfrogs than male toads themselves.