Intra-individual variation in the vocalized frequency of the Taiwanese leaf-nosed bat, Hipposideros terasensis, influenced by conspecific colony members

We examined the intra-individual variation in resting frequency of the constant-frequency component of the second harmonic of the pulse (F _rest) over 4 years in a laboratory colony of the Taiwanese leaf-nosed bat (Hipposideros terasensis). Patterns of change in F _rest were observed when individuals were added to or removed from the colony so that we investigated whether F _rest was affected by neighboring colony members. F _rest of each bat continually showed a long-term gradual change throughout the year, and all bats in the colony increased or decreased their F _rest in the same direction as a group non-seasonally. The greatest short-term changes were observed when new bats with a relatively low F _rest joined the colony and F _rest of new bats converged with those of the original colony members around 8 –16 days after their introduction. Conversely, a single individual showed sudden short-term decrease in F _rest after its isolation from other colony members. These findings strongly indicate that F _rest is flexible according to the presence of neighboring conspecific bats. We suggest that the audio-vocal feedback for conspecific pulses appears to be involved in the short- or long-term intra-individual variation in F _rest other than factors previously thought such as age or season.