Snake-like bird hisses induce anti-predator responses in a frog

Mimicry is a fascinating natural phenomenon, yet the ecological role of vocal mimicry receives limited attention. Some snakes emit hissing calls and many birds perform such acoustic mimicry in order to deter potential predators. Here we hypothesize that snake-like hisses may evoke anti-predator responses in anuran species. We conducted sound playbacks to test how little torrent frogs (Amolops torrentis) varied their behaviors in response to white noise, snake hisses, and snake-like bird hisses. We found that snake hiss from sympatric king cobras (Ophiophagus hannah) could change calling behavior of little torrent frogs, while white noise and snake hiss from allopatric Gaboon vipers (Bitis gabonica) showed no influence. Calling frogs also had no response to white noise and great tit (Parus major) hisses, which had low acoustic similarity with snakes, while they decreased calling activity when exposed to zitting cisticola (Cisticola juncidis) hisses which had high acoustic similarity with snakes. In addition, more individuals cease calling during the playback of zitting cisticola hisses. These results suggest that both snake and snake-like hiss calls may evoke anti-predator responses in frog species. To our knowledge, this is the first study that attempts to reveal the effect of snake calls and avian vocal mimicry on anurans.