Gekko are common nocturnal lizards in Japan. Some of them co-occur without causing hybridization, whereas some species hybridize with sympatric congeners. The previous study of male vocalization strongly suggested that males of the species have species-specific pattern calls may use them for species recognition, whereas the species do not have any patterns in the calls may not discriminate the species by the calls. To confirm this prediction, I conducted the call playback experiments using G. hokouensis and Gekko sp. B which have each species-specific pattern calls, and G. yakuensis which have patternless calls. In both species-specific pattern call species, G. hokouensis and Gekko sp. B, discriminated the conspecific call from sympatric congener’s call and preferred conspecific call. On the other hand, the patternless call species, G. yakuensis did not discriminate the conspecific call from sympatric congener’s call. These results supported the above prediction. Considering the asymmetric species recognition in Gekko species, it is suggested that the hybridization is caused by the loss of species recognition system in females of patternless call species. The species recognition system in the calls may be the critical factor that determines whether two Gekko species fuse or maintain the species identity when they contact secondarily.