Golden Langur Habitat Shrinking Due to Deforestation in Assam, Experts Warn

The endangered golden langur (Trachypithecus geei) is facing a severe threat to its survival due to widespread deforestation and habitat loss in Assam. Experts warn that the species, which is endemic to the Indo-Bhutan border, is experiencing rapid population decline as forests are being cleared for agriculture and human settlements.

Dr. Jihosuo Biswas, a senior primatologist at the Primate Research Centre Northeast India (NGO), pointed out that the main driver behind this habitat destruction is deforestation, further intensified by the expansion of farmland and infrastructure development. The golden langur, an arboreal species primarily found in four districts of western Assam and six districts of south-central Bhutan, has seen more than half of its Indian habitat disappear, particularly in the Kokrajhar and Bongaigaon districts.

“This habitat loss has led to the fragmentation of once vast forest areas into smaller, isolated fragments, jeopardizing the survival of the golden langur population in these regions,” said Dr. Biswas. He explained that the fragmentation, coupled with the construction of roads and other infrastructure, has forced langurs to engage in risky terrestrial behaviors, leading to increased mortality from road accidents and exposure to predators.

Dr. Biswas also highlighted the physiological stress faced by golden langurs due to their fragmented habitats. "Linear infrastructure developments have severely impacted connectivity between forest fragments, resulting in altered home ranges, higher stress levels, and an increased risk of parasitic infections among the primates," he added.

Road accidents are becoming a leading cause of death for golden langurs in the region. Since 2013, Dr. Biswas and his team have recorded numerous instances of road kills, electric hazards, and rising parasitic infections in key areas such as Nadangiri RF, Nayekgaon PRF-Rubber Garden-Baxamara-Amguri, and Chakrashilla Wildlife Sanctuary. "Wildlife electrocutions and road kills have significantly impacted the golden langur population in urban areas," he noted.

A recent study conducted by Dr. Biswas's team examined the traffic and locomotion patterns of golden langurs along the SH-14 highway. "Our research found that in 71% of road crossings, golden langurs chose to cross at ground level, risking collisions with vehicles. Only 29% of the time did they use existing canopy connectivity to avoid danger," said Dr. Biswas.

To address these dangers, Dr. Biswas and his team initiated a project to construct artificial canopy bridges (ACB) across fragmented forest areas in the Nayekgaon-Rubber Garden-Baxamara-Amguri forest complex. These bridges aim to provide golden langurs with safe passage across roads. "We used high-density polyethylene (HDPE) pipes, which are durable, environmentally friendly, and cost-effective, to construct the bridges," Dr. Biswas explained. He further stated that two bridges have already been installed, with camera traps monitoring their usage.

In addition to pipe bridges, the team also constructed ladder bridges at their field station in Siljan, Kokrajhar. "It took six months for the golden langurs to start using the ladder bridges, but their adoption of these safe passageways has been promising," said Dr. Biswas.

Between June 2022 and February 2024, 17 road collisions involving golden langurs were documented along the SH-14 highway. Tragically, six of these incidents resulted in fatalities, while others left the animals with serious injuries, including broken limbs and amputations.

To foster local support, the research team has been working with communities to plant trees and restore natural corridors between fragmented habitats. This initiative aims to reconnect the isolated forest patches, allowing for future population exchanges of golden langurs in the Nadangiri-Baxamara-Amguri-Nayekgaon-Chakrashilla forest complex.

As habitat loss and infrastructure development continue to threaten the survival of golden langurs, conservation efforts, such as canopy bridges and habitat restoration, offer a glimmer of hope for this endangered species.

Also Read: Golden Langur Electrocuted in Assam’s Bongaigaon, Power Dept Faces Backlash