Time Course of Vocal Modulation During Isolation in Common Marmosets (Callithrix jacchus)

Chieko Yamaguchi, Akihiro Izumi, Katsuki Nakamura

状況の変化に応じたコモンマーモセットの音響特性の時間的変化について検討した。3種類の異なる隔離場面におけるPheeの音響特性を調べたところ、異なる種類の音響パラメータごとに異なる時間的変化パターンがみられた。発声頻度と音量については、ペア個体が連れ去られるのを見た直後に急激な上昇がみられ、続いて徐々に減少した。一方で音声の持続時間は、相手からの音声応答がない条件において、一貫して長かった。相手から返事がある場合に音声を短くすることは、音声交換において相手の音声との重複を避けることに役立つと考えられる。これらのことから、マーモセットが社会的状況に応じて音響特性を調節していることが示唆された。

American journal of primatology, 72: 681-688, 2010

Common marmosets vocalize phee calls as isolation calls, which seem to facilitate their reunion with family groups. To identify multiple acoustic properties with different time courses, we examined acoustic modulations of phees during different social contexts of isolation. Subject marmosets were totally isolated in one condition, were visually isolated and could exchange vocalizations in another condition, and were visually isolated and subsequently totally isolated in a third condition. We recorded 6,035 phees of 10 male–female marmoset pairs and conducted acoustic analysis. The marmosets frequently vocalized phees that were temporally elongated and louder during isolation, with varying time courses of these changes in acoustic parameters. The vocal rates and sound levels of the phees increased as soon as the marmosets saw their pair mates being taken away, and then gradually calmed down. The phee duration was longer in conditions during which there were no vocal responses from their pair mates. Louder vocalizations are conspicuous and seem to be effective for long-distance transmission, whereas shorter call duration during vocal exchanges might avoid possible vocal overlap between mates.

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