The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

New population estimates of Pagai Island, Mentawai, West Sumatran primates


1Biology, Randolph C. College, 2Honors Program, Wake Tech.

Friday 2:15-2:30, Parlors Add to calendar

The four primates that inhabit the Mentawai Islands - Kloss’s gibbon (Hylobates klossii), the Mentawai pig-tailed macaque (Macaca pagensis), the Mentawai Island leaf langur (Presbytis potenziani), and the simakobu monkey (Simias concolor) - are endemic and endangered. In this study, previous estimates of the population sizes of these primates on two islands - North Pagai and South Pagai – were revised. Forest cover was determined by using Google Earth Pro composite satellite imagery, which recently was updated (Google, 2010). Forested areas were differentiated from unforested and developed areas by color (dark green vs. lighter hues). The forested sections were outlined with the Google Earth Pro polygon tool, and the areas of the polygons were calculated to one hundredth of a unit. This information was used to compute the amount of remaining forest on each island.

To calculate population estimates, the average densities of each species (from Paciulli, 2004) was multiplied by the amount of forested area. This yielded an estimate of the total number of individuals on each island. The estimates for the two islands were added together to obtain population estimates for both islands. The results indicate that there are approximately 299 Kloss’s gibbons, 2276 pig-tailed macaques, 440 leaf monkeys, and 954 simakobus on the Pagai Islands. These numbers, when compared to previous population estimates of the Mentawai primates, demonstrate drastic reductions in population sizes. One of the most obvious reasons for this decline appears to be considerable habitat loss.

This research was funded generously by Wildlife Conservation Society and Primate Conservation, Inc.

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