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 3,500 km2 to 2,400 km2 and the southern Mentawai islands of Sipora and Pagai have decreased from 1300 km2 to 300 km2. 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 logging and conversions to commercial palm oil plantations through concessions and illegal activities. Many of the areas in the southern Mentawai islands have experienced heavy logging operations that have left little forestry for the Mentawai primates. Most of the forestry has now been reduced from primary forestry to secondary forestry which is troubling since the pig-tailed langur thrives in arboreal environments.
The reduction on forestry in the southern Mentawai islands creates a domino effect of paving new land for more human activities and settlement. The second main factor associated with the population decline of this species is hunting. Local inhabitants have historically used arrows and poisonous materials to hunt this species. However technological advancements of firearms have facilitated the hunting of this species, especially since it is one of the largest primates on these islands. Many local inhabitants hunt this species because it is considered a delicacy, with many locals saying it has the best tasting meat compared to other primates. Population density data suggests that an increase in hunting pressure at survey sites results in lower population densities of this primate.
Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422
Schwitzer, 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
Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y
Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier)
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Tenaza, Richard R. (1989). "Female sexual swellings in the Asian colobine Simias concolor". American Journal of Primatology. 17 (1): 81–86. doi:10.1002/ajp.1350170108. ISSN 0275-2565. PMID 31968853. S2CID 83904665. https://onlinelibrary.wiley.com/doi/10.1002/ajp.1350170108
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
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.
Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Lanjouw, Annette (2021). "De-colonizing conservation in a global world". American Journal of Primatology. 83 (4): e23258. doi:10.1002/ajp.23258. ISSN 0275-2565. PMC 8244066. PMID 33764605. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8244066
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
Tenaza, Richard R. (1989). "Female sexual swellings in the Asian colobine Simias concolor". American Journal of Primatology. 17 (1): 81–86. doi:10.1002/ajp.1350170108. ISSN 0275-2565. PMID 31968853. S2CID 83904665. https://onlinelibrary.wiley.com/doi/10.1002/ajp.1350170108
Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X
Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X
Erb, Wendy M.; Borries, Carola; Lestari, Nurul S.; Hodges, J. Keith (2012-12-01). "Annual Variation in Ecology and Reproduction of Wild Simakobu (Simias concolor)". International Journal of Primatology. 33 (6): 1406–1419. doi:10.1007/s10764-012-9630-3. ISSN 1573-8604. S2CID 14982894. https://doi.org/10.1007/s10764-012-9630-3
Erb, Wendy M.; Borries, Carola; Lestari, Nurul S.; Hodges, J. Keith (2012-12-01). "Annual Variation in Ecology and Reproduction of Wild Simakobu (Simias concolor)". International Journal of Primatology. 33 (6): 1406–1419. doi:10.1007/s10764-012-9630-3. ISSN 1573-8604. S2CID 14982894. https://doi.org/10.1007/s10764-012-9630-3
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y
Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y
Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier)
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml
Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422
Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422
Schwitzer, 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
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full
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.
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.
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.
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier)
Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier)
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.
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full
Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full
Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full
Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full
Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203.
Lanjouw, Annette (2021). "De-colonizing conservation in a global world". American Journal of Primatology. 83 (4): e23258. doi:10.1002/ajp.23258. ISSN 0275-2565. PMC 8244066. PMID 33764605. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8244066
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.
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.
Schwitzer, 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
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.
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.
Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. p. 175. ISBN 0-801-88221-4. OCLC 62265494. 0-801-88221-4