SUBMISSIVE PANT–GRUNT GREETING OF FEMALE CHIMPANZEES IN MAHALE MOUNTAINS NATIONAL PARK, TANZANIA

概要

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One of the unique greeting behaviors of chimpanzees (Pan troglodytes) is pant–grunt vocalization, which is given only by lower-ranking individuals toward a more dominantgroup member. It is a typical social behavior performed when adult females encounter adultmales. Previous studies have proposed some social functions of pant–grunts, such as signalingsubmission, signaling appeasement, expressing support, and checking tolerance. To evaluatethe social variables driving pant–grunts, I investigated pant–grunts by adult female chimpanzeesof the M group in Mahale Mountains National Park, Tanzania. I found that pant–gruntsfunctioned as a submissive signal between adult males and females, but did not always occurduring encounters of adult females with adult males. Whether the pant–grunt functions as anappeasement signal remains unclear, but adult females performed pant–grunts as a reaction tothe aggression of other individuals. Adult females did not express their support for a particularmale by pant–grunting during the study period, probably because the dominance rank amongadult males was stable. Rather than checking tolerance at the time, maintaining relations withadult males by pant–grunting was more essential for adult females. Whether adult femalesperformed pant–grunts during encounters with adult males depended on the individuals present,the social power balance, and the current social interactions.
2011-04-28