Females and males respond differently to calls impaired by noise in a tree frog.

Both human and nonhuman animals communicating acoustically face the problem of noise interference, especially anurans during mating activities. Previous studies concentrated on the effect of continuous noise on signal recognition, but it is still unknown whether different notes in advertisement calls impaired by noise affect female choice and male-male competition or not. In this study, we tested female preferences and male-evoked vocal responses in serrate-legged small tree frog (), by broadcasting the five-note advertisement call and the advertisement call with the second, third, or fourth note replaced by noise, respectively. In phonotaxis experiments, females significantly discriminated against the advertisement call with the fourth note impaired by noise, although they did not discriminate against other two calls impaired by noise, which indicates that the negative effect of noise on female preference is related to the order of impaired notes in the advertisement call. In playback experiments, males increased the total number of notes in response to noise-impaired calls compared with spontaneous calls. More interestingly, the vocal responses evoked by noise-impaired calls were generally similar to those evoked by complete advertisement calls, suggesting that males may recognize the noise-impaired calls as complete advertisement calls. Taken together, our study shows that different notes in advertisement calls replaced by noise have distinct effects on female choice and male-male competition.