HOPE report

Number:19-015-2

Ecology of proboscis monkeys (Nasalis larvatus) in Sabah, Malaysia

Report:Matsuda Ikki

Date:2008/03/09 - 2008/03/24

To clarify the ecology of proboscis monkeys, we have focused on studying one harem group in Lower Kinabatangan Wildlife Sanctuary since January 2005. Behavioral data of the harem group have been collected by a Malaysian local assistant while the researcher is absent from the study site. In November 2007, when the researcher was absent, the -male in the focal group was replaced. During the study period (9-24 March 2008), since the river's water level was very high due to seasonal flooding, I could not observe the monkeys in the forest. I observed and identified several proboscis monkey groups from boat in late afternoon, and the interaction between harem groups was clearly observed at the riverside trees.
In addition to the research in my study site, I visited Danau Girang which is located 60 km upstream from the site and observed proboscis monkeys there to explore the possibilities of a comparative study of individuals inhabiting different sites. The vegetation patterns in Danau Girang are similar to my study site, but there are several oxbow lakes where the monkeys sleep over night. The land usage of proboscis monkeys in Danau Girang is thought to be different from that in my study site. I also visited Klias and conducted a boat census along the Klias river (length 12 km) and found 7 harem groups and 1 all-male group. The vegetation in Klias is mostly mangrove forest and differs greatly from that of my study site, speculating that the proboscis monkeys in Klias have a different feeding strategy from that of the monkeys observed in my study.


Infant in Lok Kawi Wildlife Park


Adult female monkey in focal group

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