areas. In the 1980s population estimates of the Pig-tailed langur was 19,000 on the island of Siberut and 26,000 across all four islands. In 2004 Lisa M. Paciulli dedicated their PhD dissertation towards studying threats to Mentawai island primates and determining population densities associated with logging pressures. Population estimates were found to be around 6,700-17,300 across all islands with a large amount of variation being attributed due to hunting and logging pressures. Population densities were 2.5 individuals/km2 in logged areas whereas unlogged areas had a population density of 5 individuals/km2. An extensive population density survey was conducted by the University of Indonesia on four endemic Mentawai primates. This research was exclusive to the southern Mentawai islands and included a variety of survey areas, most of which devastated by commercial logging. The results of the 2008-2009 surveys are population densities of 1.5 groups/km2 on the island of Sipora and 2.1 ± 0.3 groups/km2 on the Pagai islands with group sizes around 3 individuals. Research into population densities on the northern Mentawai island of Siberut is more abundant due to the lower mean population densities of humans living on this island as well as the considerable amount of forestry that remains in comparison to the southern Mentawai islands. In northern Siberut researchers in the Peleonan forest conducted population density surveys from July to December of 2005. Results form these surveys show a mean density of 16.2 groups/km2. One of the main factors associated with the population decline of this species is habitat disturbance from commercial logging operations. Forestry cover varies significantly among the islands. The island of Siberut has most of its area declared as a National park whereas the southern islands of Sipora, North Pagai, and South Pagai have limited areas of forestry conservation. It is estimated that Siberut's forest cover decreased from 3,500km2 to 2,400km2 and the southern Mentawai islands of Sipora and Pagai have decreased from 1300km2 to 300km2. The reason for Siberut's extensive forestry cover in comparison to the southern islands is due to historical conservation efforts. Much of the efforts started in the 1980s with the help of UNESCO man and the Biosphere reserve. This was expanded in the 1990s were a large portion of Siberut was declared a National Park. The declaration of this National Park allowed for hunting and logging operations to be significantly reduced; although areas around the national park still experience pressures of