Primatologists and conservation organizations have launched a 10-year action plan to improve the outlook for langur monkeys in the Sundaland biodiversity hotspot, a region of Southeast Asia that spans Brunei, Indonesia, Malaysia, Myanmar, Singapore and Thailand.

Asian langurs, a group of 20 species in the genus Presbytis, are in steep decline across Southeast Asia due to habitat loss, hunting and retaliatory killings triggered by crop-raiding conflicts, said action plan co-author Andie Ang, a researcher at Singapore-based Mandai Nature. The medium-size arboreal monkeys face particularly severe pressure in the Sundaland region, she noted.

“Sundaland has among the world’s highest deforestation rates: over 50% of forest cover [has] been lost since 1970, fragmenting langur habitats,” Ang, who is also deputy chair of the primate specialist group at the IUCN, the global wildlife conservation authority and part of the consortium behind the plan, told Mongabay.

As the first ever conservation framework targeting an entire genus of threatened monkeys in Asia, Ang said the new plan will help to make the most of limited conservation resources. “By focusing on Sundaland — a region of both crisis and opportunity — the plan maximizes impact for langurs and ecosystems alike,” she said.

The drivers of forest loss vary across the Sundaland region, from expansion of oil palm monoculture in Borneo, to road construction, urban encroachment and forest fires in Sumatra. The impacts on langur numbers have been just as devastating.

According to the IUCN Red List, 24 of the 28 types of langur found across Sundaland are threatened with extinction. Two species — the Bornean banded langur (Presbytis chrysomelas) and the Raffles’ banded langur (P. femoralis) — are also classified by the IUCN as among the world’s 25 most endangered primates.

Exposure to poaching

Langurs are leaf-eating monkeys that spend most of their lives high in the forest canopy. Their multichambered guts allow them to digest tough plant material, but being so exceptionally well-adapted to life in the trees makes them especially vulnerable to deforestation. Besides direct habitat loss, subpopulations confined to shrinking pockets of forest quickly become genetically isolated and more prone to extinction. Crucially, these smaller groups are also more exposed to poaching.

Poaching is driven by demand for langurs as pets as well as for their body parts and bezoar stones: small mineral deposits that sometimes accumulate in their stomachs and are prized by humans for use in traditional medicines. They’re also hunted for their meat in many parts of their range, a practice that can quickly become unsustainable when coupled with habitat loss.

“Capturing for the pet trade is a challenge — several species do very poorly in captivity because of their specialized diet and needs and they quickly die,” Vincent Nijman from the Oxford Wildlife Trade Research Group at Oxford Brookes University, U.K., told Mongabay in an email. “These wild animals are not suitable as pets: people should get a gerbil or a cat.”

Commercial poaching for traditional medicine ingredients like bezoar stones can quickly decimate local populations, Nijman said: “It can be devastating, wiping out entire groups.” His own research documented a 50-80% decline in a Hose’s langur (P. hosei) population in East Kalimantan, Indonesian Borneo, between 1996 and 2003, even though their forest habitat remained mostly intact. Interviews with local people revealed the decline was triggered by excessive hunting of the monkeys after a single merchant offered to buy bezoar stones from villagers.

Stanislav Lhota, a primatologist at the Czech University of Life Sciences, who has also studied primates extensively in the region, said the constantly shifting nature of traditional medicine markets makes it difficult to manage. “You never know where such a single merchant appears and which population will be wiped out next,” he said. “That means that even sustainable subsistence hunting [for meat] represents a hidden threat, because it helps to preserve the hunting skills and habits, which may turn out to be detrimental at some unknown future point of time.”

The illegal trade persists despite national wildlife laws and international regulations that protect many species of langur from commercial trade, at least on paper. Poor enforcement of existing laws due to a lack of understanding and awareness of langurs are to blame, according to Nijman.

“In several countries … trading or killing [langurs] is not really seen as a serious offence,” Nijman said. However, removing langurs from landscapes has far-reaching implications not just for individual animals but for entire ecosystems, he noted. As key tree seed predators, langurs help to maintain the balance in healthy forests. Therefore, the langur trade “should be seen as an environmental crime or even an economic one,” Nijman said.

Key measures for langurs

The new action plan brings together the expertise of more than 30 primate specialists who convened during the 29^th International Primatological Society Congress in Kuching, Malaysia. Together, they identified the key measures needed to reverse population declines and to recover species on the brink of extinction.

They identified nine priority areas, including: strengthening protection and connectivity of key langur habitats; improving legal protection measures; fostering community-based tourism to reduce hunting pressure; developing best practice guidelines for captive care; and implementing awareness-raising campaigns.

Raising public awareness about their protected status and cultural and ecological importance will be important to gain the support of local communities for long-term conservation. Some species are revered locally as forest guardians, while in places like Sabah in Malaysian Borneo, langurs draw tourists to remote areas. As Ang puts it: “They’re worth far more alive than hunted.”

The authors also underscore the need for further research on poorly known species and the challenges they face. “We probably do not know about many populations that would warrant protection, and many habitats are destroyed and local populations hunted to extinction without us even realizing that they existed,” Lhota said.

With the conservation actions defined, it will now be up to conservation groups, governments, local communities, academics, zoos and wildlife centers to translate them into work on the ground. Engaging with the private sector will also be key, according to Ang — encouraging palm oil firms to support more sustainable practices, for instance, and promoting langur-friendly tourism activities.

Toward funding and action

In an effort to raise further awareness about langurs’ plight, the team behind the plan created “International Colobine Monkey Day,” to be celebrated annual on Aug. 25. Langurs belong to the subfamily Colobinae, which includes other medium-size leaf-eaters such as snub-nosed monkeys and African colobus monkeys. Like many such campaigns, Colobine Monkey Day aims to spotlight the importance of protecting these monkeys, as well as highlight the dangers they face.

Ang said she hopes these efforts spur policymakers and donors into taking action to prevent extinctions, expand protected areas, restore habitat corridors, and change the way people perceive langurs so that they’re viewed as assets rather than pests.

Chris Hallam, head of wildlife and counter wildlife crime at WWF-Asia Pacific, said he welcomed the launch of a dedicated conservation action plan as a “vital starting point” to bring attention to langurs, drive funding, and devise more targeted actions in range countries.

“Most of these species are lower on national priorities for action than their more showy cousins like orangutans or non-primate species like tigers and elephants,” Hallam told Mongabay. “It’s great to see this type of effort for such a threatened and under-appreciated but ecologically significant group.”

Fully implementing the plan will require considerable conservation capacity and mobilization of funds, which are not always accessible for lesser-known species like langurs. However, Hallam noted promising options, such as the Global Biodiversity Framework Fund, which aims to mobilize $20 billion annually for biodiversity in developing countries, and growing awareness of biodiversity among the private sector.

“Highlighting Asian langurs, their variety and beauty, and their important role in ecosystems on which people depend, can hopefully help resource the conservation actions needed for these species now and into the future,” Hallam said.

Banner image: A Raffles banded langur. Image courtesy of Andie Ang.

Carolyn Cowan is a staff writer for Mongabay.

Citations:

Nijman, V. (2005). Decline of the endemic hose’s langur Presbytis hosei in Kayan Mentarang National Park, East Borneo. Oryx, 39(2), 223-226. doi:10.1017/S0030605305000475

See related story:

Langurs in Bangladesh face extinction as hybridization between species escalates

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