[4] As an arboreal primate the pig-tailed langur spends most of its time in the canopy devoting the majority of its activity budget towards resting and feeding.

This can largely be attributed to the difference in conservation efforts as much of northern Siberut has been declared a national park whereas the southern islands have historically been devastated by commercial logging.

The reduction in forest cover has allowed for greater levels of human activity and settlement which facilitates hunting, especially in the southern islands where most areas are unprotected.

[7] Sexual swelling is exhibited by this species which is rare for single male multi female groups of Colobinae monkeys.

[9] Many researchers would like to reclassify this species into the Nasalis genus but phylogenic analyses suggest that these two groups should remain in their separate sister taxa.

[11] The Critically Endangered status of this primate gives even more reason for it to remain under the genus Simias since the grouping of these genera could affect conservation efforts.

[5] The activity budget of this primate is mostly resting and feeding with a small fraction of time devoted towards travel and social behavior.

[7] The reason for different group sizes is not factually known, however many researchers suggest that it could be due to anthropogenic factors such as hunting and deforestation.

[3] It is among The World's 25 Most Endangered Primates due to the many anthropogenic pressures it faces on the islands[4] which include, destruction of forest for commercial use, hunting and illegal pet trade.

[14] In 2004 Lisa M. Paciulli dedicated their PhD dissertation towards studying threats to Mentawai island primates and determining population densities associated with logging pressures.

[10] 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.

[14] The reason for Siberut's extensive forestry cover in comparison to the southern islands is due to historical conservation efforts.

[8] The reduction on forestry in the southern Mentawai islands creates a domino effect of paving new land for more human activities and settlement.