Tinsukia: The endangered Capped langur (Trachypithecus pileatus) is rapidly disappearing from fragmented rainforest patches in Assam’s Upper Brahmaputra Valley, according to a study published in the Journal of Asia-Pacific Biodiversity.
The species, locally known as Tupimuria Bandor, was found surviving in only 11 of the 40 forest fragments surveyed, highlighting the impact of sustained habitat fragmentation across the region.
The paper, titled “Lost in Fragmentation: Occurrence of Capped Langur Trachypithecus pileatus in Upper Brahmaputra Valley of Assam”, was authored by Neeharika Gogoi, Samrat Sengupta, Bijay Basfore and Narayan Sharma. The researchers conducted field surveys between February 2019 and January 2020 across lowland forest patches in the valley.
They recorded 82 individuals, including adults, juveniles and infants, distributed across isolated fragments. Seven forest patches where the species had been reported earlier showed no presence during the survey, indicating local extirpation.
Large tracts of what were once contiguous tropical lowland forests have been reduced to disconnected patches over the years due to agricultural expansion, tea plantations, infrastructure projects and human settlements. The study notes that fragmentation has altered both habitat structure and food availability.
Food tree diversity emerged as the strongest predictor of langur presence. Forest fragments with a higher diversity of native leaf- and fruit-bearing trees were more likely to support viable groups. Degraded patches with fewer food resources showed reduced or absent populations.
In some areas, langurs were observed foraging and resting near human habitations, a shift that increases exposure to threats such as electrocution from power lines, road accidents and attacks by stray dogs.
The authors call for restoration of degraded forest patches, protection of fragments with high food tree diversity and the creation of ecological corridors to reconnect isolated habitats. Without coordinated conservation measures at the landscape level, the study cautions that the species may continue to decline in one of its key habitats in Assam.