This species is classified as Critically endangered by the International Union for Conservation of Nature.Quinten, M, Setiawan, A., Cheyne, S., Traeholt, C. & Whittaker, D. 2020. Simias concolor. The IUCN Red List of Threatened Species 2020: e.T20229A17953422. It was classified as Endangered (IUCN status) up until 2008 were the endangerment status was changed to Critically Endangered. It is among The World's 25 Most Endangered Primates due to the many anthropogenic pressures it faces on the islandsSchwitzer, C., Mittermeier, R.A., Rylands, A.B., Chiozza, F., Williamson, E.A., Byler, D., Wich, S., Humle, T., Johnson, C., Mynott, H., and McCabe, G. (eds.). 2019. Primates in Peril: The World’s 25 Most Endangered Primates 2018–2020. IUCN SSC Primate Specialist Group, International Primatological Society, Global Wildlife Conservation, and Bristol Zoological Society, Washington, DC. 57-58pp which include, destruction of forest for commercial use, hunting and illegal pet trade.Yanuar, A., & Supriatna, J. (2018). The Status of Primates in the Southern Mentawai Islands, Indonesia. Primate Conservation, 32, 193–203 Population size estimates have been conducted across many years with varying islands being chosen for research 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.Paciulli, L. M. 2004. The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates. PhD thesis, State University of New York, Stony Brook. 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.
