Conspecific Influences on Vigilance Behavior in Wild Chimpanzees |
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Authors: | Nobuyuki Kutsukake |
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Institution: | (1) Department of Cognitive and Behavioral Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan;(2) Department of Biological Sciences, Graduate School of Sciences, The University of Tokyo, Tokyo, Japan;(3) Laboratory for Biolinguistics, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama, Japan |
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Abstract: | Diurnal primates rely on visual monitoring behavior to collect various kinds of ecological and social information. Vigilance
behavior is monitoring specifically to detect external threats. Previous studies of vigilance behavior were focused mainly
on the influence of predation threats, whereas the influences of conspecific factors, such as intragroup threats, have been
relatively unstudied. Individual vigilance is predicted to be inversely related to the group size or the number of individuals
nearby if the main target of the vigilance is a predation threat and positively related if the main target of the vigilance
is a conspecific threat. I studied wild chimpanzees (Pan troglodytes schweinfurthii) in Mahale Mountains National Park, Tanzania, and measured the vigilance duration when they are resting on the ground via
2-min focal observation. In both males and females, vigilance duration increased as the number of individuals nearby increased.
This result agrees with the idea that the chimpanzees are vigilant toward other group members. In addition, maternal vigilance
monitors and protects the safety of dependent offspring as the duration of maternal vigilance was longer when a dependent
infant was separated from its mother than when the offspring was in contact with its mother. The results indicate that the
vigilance behavior in wild chimpanzees was affected by conspecific factors. |
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Keywords: | chimpanzee conspecific monitoring group size effect predation vigilance |
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