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 (Frest) over 4 years in a laboratory colony of the Taiwanese leaf-nosed bat (Hipposideros terasensis). Patterns of change in Frest were observed when individuals were added to or removed from the colony so that we investigated whether Frest was affected by neighboring colony members. Frest of each bat continually showed a long-term gradual change throughout the year, and all bats in the colony increased or decreased their Frest in the same direction as a group non-seasonally. The greatest short-term changes were observed when new bats with a relatively low Frest joined the colony and Frest 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 Frest after its isolation from other colony members. These findings strongly indicate that Frest 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 Frest other than factors previously thought such as age or season.
KeywordsHipposideros terasensis CF-FM bats Echolocation Resting frequency Intra-individual variation
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