This species is listed under CITES Appendix I, as well as under Appendix IB of Decree 32/2006 and Appendix I of Decree 160/2014 in Viet Nam and is protected under The Law on Forestry NS/RKM/0802/016, article 49, identified as Pygathrix nemaeus in Prakas 020 PR.MAFF in Cambodia.
It is known to occur in several protected areas in Cambodia including Mondulkiri Protected Forest, Seima Biodiversity Conservation Area, Snuol Wildlife Sanctuary, Phnom Prich Wildlife Sanctuary (Pollard et al. 2007; BirdLife unpubl. data; Rawson, 2010; Timmins and Ou Rattanak 2001; Walston et al. 2001). In Viet Nam, the species is recorded in Bu Gia Map National Park (NP), Cat Tien NP, Nui Chua NP, Bidoup – Nui Ba NP, Chu Yang Sin NP, Lo Go-Xa Mat NP, Ta Dung Nature Reserve (NR), Nam Nung NR, Takou NR, Hon Ba NR (Nadler et al. 2003, Hoang Minh Duc 2007, Hoang Minh Duc et al. 2010).
Recommended actions for the conservation of this species in Viet Nam include 1: Control of illegal wildlife trade in Black-shanked Doucs throughout this species range. 2: Improve development planning and environmental impact assessment to mitigate the impacts on development on Black-shanked Douc habitats. In Cambodia improved enforcement on illegal timber removal is needed to protect the Douc habitats.
The species is found in northeastern Cambodia and southern Viet Nam. Recent fieldwork has demonstrated that populations of this species are quite widespread across this range (Lippold 1995, Hoang Minh Duc 2007, Rawson 2009). In Cambodia, they are found only east of the Mekong with the northerly extent to about 14°00' N in Voensei District, Ratanakiri Province, where the species is possibly sympatric with Pygathrix nemaeus (Rawson and Roos 2008). In southern Viet Nam, this species has a fragmented distribution extending from Chu Prong district (13°30' N, Gia Lai Province) in the north to Ta Kou Nature Reserve (10°48' N, Binh Thuan Province) in the south.
This species occurs in several southern Vietnamese provinces including Phu Yen, Khanh Hoa, Dak Lak, Dak Nong, Lam Dong, Ninh Thuan, Binh Thuan, Dong Nai, Binh Phuoc, and Tay Ninh (Nadler et al. 2003, Hoang Minh Duc et al. in prep). The largest populations occur in Bu Gia Map National Park (Binh Phuoc), Nui Chua National Park (Ninh Thuan), Phuoc Binh National Park (Ninh Thuan), and Cat Tien National Park (Dong Nai and Lam Dong). Smaller populations are found in several other protected areas and state forest enterprises in this region of Viet Nam.
Cambodia, Viet Nam
The largest known population exists in Seima Biodiversity Conservation Area, Mondulkiri Province, Cambodia, where distance estimates provide a population estimate of approximately 42,000 individuals (95% confidence interval of 27,309–66,460) (Pollard et al. 2007). The densities found in Seima are probably close to carrying capacity for the species in such habitat (Rawson 2009). The largest known population in Viet Nam may be in Bu Gia Map NP (Binh Phuoc Province) which is estimated at 1,789 individuals (1,306–2,462, 95% CI) (Hoang Minh Duc et al. in prep). Other stronghold for the species are recorded in Nui Chua National Park (Ninh Thuan Province), which is estimated at 500-700 individuals (Hoang Minh Duc and Ly Ngoc Sam 2005), Phuoc Binh NP at least 164 individuals (Hoang Minh Duc 2007), Chu Prong (Gia Lai Province) at about 200 to 250 individuals (Nadler 2010), Hon Heo Peninsula (Khanh Hoa Province) with about 155-180 individuals (Nguyen Ai Tam 2008), Cat Tien National Park at about 109 individuals (Phan Duy Thuc et al. 2005), and Takou Nature Reserve is about 64 individuals (Hoang Minh Duc et al. 2010). In southern Viet Nam, this species survives in many small, isolated forest fragments, in comparison with the situation with the Red-shanked Doucs in the north, where the species is not able to persist in small forest fragments.
In southern Viet Nam, this species survives in many small, isolated forest fragments, differing from the situation with the Red-shanked Doucs in the north, where the species is not able to persist in small forest fragments.
The key threats to the taxon include hunting for traditional medicine and local consumption and loss and fragmentation of forest habitats due to legal and illegal logging, conversion for agriculture, and construction of roads and hydroelectric dams.
Hunting is currently the major threat to this species (Nadler et al. 2003). It is most often hunted for traditional “medicine”. Between 2008 and 2013 there were a confirmed total of at least 577 Black-shanked Doucs being poached/traded in Viet Nam (Beyle et al. 2014). The real number would be much higher since the number of wildlife trade/hunting cases documented in Viet Nam was estimated at about 10 to 20 percent of the total cases (UNODC 2015). Thus, the number of Black-shanked Doucs being killed/traded in that period is likely between 2,885 and 5,770 individuals.
Destruction of its natural habitat is also a threat to this species; a large portion of central and southern Viet Nam suffered from massive wartime damage, and the post-war human demographic explosion and extensive logging for coffee, rubber, and cashew plantations have reduced its natural habitat. Most forest at lowland elevations has been cleared and little forest remains undisturbed (Nadler et al. 2003). The resettlement of some three million people from northern Viet Nam to the central highlands is likely to exacerbate rates of habitat loss through the Vietnamese range of the species. Within the range of the species in Viet Nam, natural forest loss was more than 520,000 ha between 2002 and 2016 (MARD 2020). Global Forest Watch (GFW 2020) reports that the within the range of Black-shanked Doucs in Viet Nam more than 253,000 ha of humid primary forest was lost between 2002 and 2019, a decrease of more than 80% of this type of forest. Development including new road construction in Mondulkiri Province, Cambodia has been associated with a rapid increase of illegal logging that is negatively impacting habitat for the Black-shanked Doucs. Global Forest Watch (GVW, 2020) reports that Mondulkiri and Ratanakiri Provinces, the two provinces home to most of this species in Cambodia, lost more than 147,000 ha of humid primary forest between 2002 and 2019, a decrease of more than 75% of this type of forest. It is likely that Viet Nam and Cambodia will continue to see significant loss of primary forests for the foreseeable future.