Intra-individual variation in the vocalized frequency of the Taiwanese leaf-nosed bat, Hipposideros terasensis, influenced by conspecific colony members
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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.
KeywordsHipposideros terasensis CF-FM bats Echolocation Resting frequency Intra-individual variation
We would like to thank Dr. Kyle Armstrong for substantial suggestions, and two anonymous reviewers for helpful and precious comments in this manuscript. This work was supported partly by a grant to RCAST at Doshisha University from MEXT of Japan, Special Research Grants for the Development of Characteristic Education from the Promotion and Mutual Aid Corporation for Private Schools, Japan, and the Innovative Cluster Creation Project promoted by MEXT. The experiments comply with the “Principles of animal care”, publication No. 86–23, revised 1985 of the National Institute of Health, and also with current Japanese laws.
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