Golden langurs killed by people, roads and power lines in Bhutan

Habitat destruction has brought the endangered primate into increasing conflict with people and infrastructure, with dwindling numbers living in fragmented areas of Bhutan and India.

golden langur Bhutan
The golden langur is one of the world’s most endangered primates and is only found in Bhutan and Assam in north-east India. Image: Balakrishnan Valappil, CC BY-SA 2.0

“In the past, we saw [golden langurs] around, but they never came near our settlements,” said Chimmi Zangmo, a 68-year-old farmer from Langthil village in central Bhutan. Now these endangered primates, found along the Mangdechhu basin, destroy vegetables and other crops, becoming a pest for local farmers.

“They never did any harm before. Now they eat our crops. It has been about three to four years since they started creating problems,” said Tshering Chuki, another farmer.

Chasing them away is nearly impossible. Langurs have started encroaching on human settlements, destroying everything that farmers cultivate in Langthil, Trongsa district.

Endangered and under attack

The golden langur (Trachypithecus geei) is one of the world’s most threatened primates – listed as endangered by the International Union for Conservation of Nature (IUCN).

There are about 6,000 golden langurs in Bhutan and over 5,000 in Assam, in north-east India, according to the most recent estimates. The population in Bhutan has declined by more than 30 per cent in the past 30 years and is expected to decline further in the near future, said Phuntsho Thinley, a wildlife biologist.

In Bhutan, hydropower activities, road construction and housing developments threaten the habitat of the golden langur.

Thinley and his team of foresters at the Ugyen Wangchuck Institute for Conservation and Environmental Research, found that these threats pose a “high risk” to langur habitat in a paper published in 2019. “Agricultural expansion, resource extraction, electrocution and roadkills had a medium impact on the habitat of the species,” the report said.

“The increasing number of humans living in proximity to langur populations in reduced, degraded and fragmented forests has resulted in langurs being killed by people and dogs or succumbing to electrocution when jumping onto power lines,” Thinley said.

Between June 2012 and June 2019, there were 107 recorded incidents in Bhutan involving golden langurs, Thinley said. This included 30 electrocutions, 15 killed on roads, 15 killed by dogs, six retaliatory killings, four road injuries and two being kept as pets.

For their research Thinley and his team carried out a survey of more than 1,000 households across protected areas of Jigme Singye Wangchuck National Park, Royal Manas National Park and Phibsoo Wildlife Sanctuary.

The team listed habitat threats from resource extraction (collection of firewood, timber, non-timber forest products, stones, boulders and sand), agricultural expansion and irrigation canals, and illegal planting of cash crops such as cardamom in forests, among others.

Most langur deaths occurred in Sarpang along the Gelephu-Sarpang road and in Zhemgang along the Dakphel-Zhemgang road and Dakphel-Tingtibi road. The Gelephu-Sarpang road is particularly dangerous because its flat terrain encourages vehicles to speed faster than 100 km/h.

Golden langurs have also died from electrocution and in road accidents looking for food beyond the reserve forests in Assam, where most of the population live outside protected areas.

Authorities in Bhutan can take immediate action to mitigate some of these threats by installing speed limit signs and speed breakers with strict enforcement of speed limits. They can also install insulated electric cables and fencing around power transformers and reduce and restrain dog populations in the primates’ core habitat areas.

Shrinking, fragmented habitat

The langur is endemic to Bhutan and the north-eastern Indian state of Assam. It is fully protected as a Schedule I species under the Forest and Nature Conservation Action of Bhutan 1995 and the Indian Wildlife Protection Act of 1972.

Its habitat is increasingly fragmented and limited to a small forest belt in western Assam and Bhutan, between the Manas river in the east, Sankosh river in the west, the foothills of the Black Mountains to the north and the Brahmaputra in the south.

In India, the species has lost about half its original habitat to encroachment, illegal tree felling, fuel wood collection and cattle grazing, according to the IUCN report Primates in Peril: The World’s 25 Most Endangered Primates 2016–2018.

Their long-term survival depends on genetic exchange; but golden langurs are now restricted to small, isolated populations through much of their range.

In Bhutan golden langurs are better protected, with about half the population located inside the three protected areas of the Jigme Singye Wangchuck National Park, Royal Manas National Park and Phibsoo Wildlife Sanctuary.

 A number of bridges built over the Mangdechhu river in the eastern part of the habitat have created corridors, allowing cross-breeding between golden langurs and capped langurs (Trachypithecus pileatus). Estimates of the number of hybrid langurs in Bhutan range from 5-15 per cent of the population.

Conservation plan needed

Despite its endangered status, there is no comprehensive conservation plan for the golden langur across its entire habitat, or specifically within Bhutan.

Conservationists say there is an urgent need to identify and rank all threats to golden langur populations, particularly in Bhutan where golden langur deaths have been increasingly documented.

Lessons from Assam

Bhutan can learn from some successful community conservation efforts in India, where habitat destruction is also the main threat to the species. Community-led conservation efforts in Manas National Park in Assam have led to a rebound in golden langur numbers and control of illegal logging and poaching. In one fragmented but protected area in a rubber plantation in Nayakgaon, Kokrajhar district of Assam, community conservation boosted langur numbers from 38 in 1997 to 52 in 2002. The population has also adapted to feeding on dry rubber seeds.

Conservationists from both countries hope legal protection of golden langur habitat and scaling up community-led conservation will help boost the population in the future.

According to Tashi Wangchuk, a researcher at the College of Science and Technology in Rinchending, Phuentsholing who did a PHD on the golden langur in Bhutan, the centralised structure of the Bhutan governmental agencies makes it difficult for them to control the country’s forests and wildlife.

“This is emphasised by the fact that 80 per cent of Bhutan’s population is rural and depends on forest resources and thus [their involvement] can make or break Bhutan’s biodiversity conservation objectives,” he wrote in a 2005 paper.

Villages need to be more involved in conservation efforts, Wangchuk argued.

His long-term recommendation was to return the traditional community forests to the local people with a system of monitoring and evaluation in place. He has developed a plan for a gradual transition from government to village control.

He hoped that in the future village groups from Assam and Bhutan can work together to jointly protect the contiguous border forests, since wildlife does not recognise political boundaries.

New guidelines to protect biodiversity

More recently, Bhutan has taken steps to improve the way it monitors biodiversity and the socioeconomic status of people who depend on biodiversity for their livelihoods. This will help improve conservation efforts across the country, said a senior forestry official, Letro, quoted in the Keunsel.

New guidelines for classifying and managing Bhutan’s key biodiversity areas were launched in August by the forest department. As well as protecting existing species, recording new species and documenting changing trends in biodiversity due to climate change and human disturbances, these guidelines will help understand threats to species including golden langurs.

This story was published with permission from The Third Pole.

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