HOPE report


Investigation of ecology and social structure of all-male group in proboscis monkeys

Report:Matsuda Ikki

Date:2009/08/16 - 2009/12/15

 To better understand ecology and social structure of proboscis monkeys, I studied all-male groups of proboscis monkeys in Lower Kinabatangan Wildlife Sanctuary from August-December 2009. It has been suggested that proboscis monkeys set up their sleeping sites in riverside trees. To confirm sleeping site locations of all-male groups, boat-based observations were conducted along the Menanggul River during late afternoon and early morning. As a result, two all-male groups were confirmed in the study site. I carefully approached one of the groups (consisting of 3 adult males and 9-12 young males) almost everyday to habituate the monkeys to researchers. During this observation, I described some physical characteristics of the group members and collected the data of social interactions among monkeys. In addition, the data of interactions among all-male and one-male groups were recorded during the study period. Further, I visited the Sabah Wildlife Department and the Institute for Tropical Biology and Conservation, University Malaysia Sabah and discussed findings from this research with Malaysian collaborators.

Adult male in all-male group

Subadult male in all-male group

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