The golden langur is in danger of extinction due to lack of suitable habitat


The golden langur, originally photographed and officially found on the east bank of the Manas River on the Bhutan-Assam border by naturalist and tea planter EP Gee in 1953, is now in desperate need of a habitat adequate. Only 13% of current habitat would be viable for the golden langur by 2031, according to a habitat suitability study of the primate, which is endemic to Assam in India and bordering Bhutan. Currently, only 18% of the species’ current ecological range of 66,320 square kilometers in the transboundary area is suitable for it. The golden langur, a species of monkey, is threatened by increasing habitat fragmentation and isolation across its range, particularly in Assam.

In India, fragmented and isolated populations of the species live in the Chirang, Kokrajhar, Dhubri and Bongaigaon districts of Assam, covering 3,950 km2, or about 5% of the state’s area. In India, the golden langur survives in the Brahmaputra valley in semi-evergreen forests, while in Bhutan it occupies the deciduous forests of the Himalayas. The study mapped the habitat suitability for the species across its entire distribution and projected its habitat suitability on the simulated landscape for the future (2031). The results predict that of the total range extent of 66,320 km2, only 12,265 km2 (18.49%) are currently suitable for the species, which will further decrease to 8,884 km2 over the next decade. , by 2031, projecting a marked reduction in its range.

Fewer than 8,000 individuals remain in the wild today in India and Bhutan; in India, 80% of this population is found outside protected areas. The golden langur (Trachypithecus geei) belongs to a large group of Old World monkeys called the colobines (subfamily Colobinae). It has a restricted range in a cross-border landscape between Bhutan and India with diverse topography and climatic and biotic components. It is one of the 25 most endangered primates in the world. It was officially described by taxonomist H. Khajuria in 1956. In Bhutan, the species is distributed in the forest habitats of Tsirang, Sarpang, Zhemgang and Trongsa districts, covering 3,486 km2, or about 9% of the area of ​​the country.

These suitable habitats are mostly scattered and fragmented across the species’ southern range. Lalit Kumar Sharma of the Zoological Survey of India, the corresponding author of the study, told Mongabay-India that most existing studies focus only on smaller areas and mainly on population estimation and behavioral research. Fewer studies were available on the details of the species’ microhabitat. “Our survey of the entire range of the species regarding habitat details and the future range of the species is the first for this endangered species. It is important to know the fate these animals will face in the near future so that appropriate conservation action can be taken,” he said. “Our study found that the species is more sensitive to landscape and patch changes than to climate change.”

An increased number of plots was noted for evergreen broadleaf forest, evergreen needleleaf forest, mixed forest, savanna, and grassland in the transboundary landscape. A decrease in the number of plots was noted for deciduous forests. These patchy and less dense land use classes show clear signs of increasing fragmentation in the landscape, leading to reduced habitat connectivity, disrupted gene flow and loss of rare alleles (reduced genetic variation) supporting local adaptation and genetic form. “Lower elevations and deciduous broadleaf forests were matched in our model as the most suitable habitat for the species. However, primates are highly adaptive species and most other forest types can be used by golden langurs if necessary. But adjustment takes time and the rate of habitat destruction or forest conversion within the species range is much higher,” said Sharma.

“The entire population of the species is also divided into two parts. A large continuous population in Bhutan and a scattered population in India in several forest patches. These forest patches are rarely protected and often insufficient to support large groups. Due to lack of food, these groups venture into human-dominated areas or cultivated fields in search of food and are often beaten in retaliation or chased and killed by local dogs,” he said. he added. The present study suggests that the golden langur is more sensitive to changes in land use and land cover than to bioclimatic factors. Rapid deforestation and illegal logging have wiped out most of the forest cover in the districts of Bongaigaon, Dhubri and Kokrajhar of West Assam, leading to a fragmented landscape.

“With more forest destroyed, each group will have fewer forest patches and smaller sizes, which can lead to a rapid decline in the species’ population,” he said. Rapid deforestation and illegal logging have wiped out most of the forest cover in Bongaigaon, Dhubri and Kokrajhar districts. The study indicates that the suitable habitats found for the species are scattered and fragmented and are vulnerable due to increasing human-caused changes leading to deforestation. Approximately 2,297 km2 of the new area beyond current suitable habitat will become livable for golden langur in the future. But most of these suitable areas are patchy and scattered across the southern range of Assam, which is most vulnerable due to increasing human changes such as agricultural and urban expansions leading to deforestation.

He said behavioral changes in both fragmented and continuous populations should be studied to observe the species’ adaptive abilities and identify the most vulnerable populations within the species’ range. “Bhutan still has a large amount of intact forest, and therefore careful management can easily secure the Bhutanese population for the species. However, the Indian population of the species must be measured very carefully. The scientific details on the ecology and species genetics should unlock many keys for the conservation of the species,” Sharma said. “The scattered distribution and fragmented population in the southern range is a concern, and the distribution is influenced by distance from patches of evergreen and broadleaf forest,” said Hillol Jyoti Singha from the Department of Zoology at Bodoland University in Mongabay-India. Singha is not associated with the study.

Singha said the study highlighted that the current range is also affected by human-induced changes, which the authors linked to declining forest cover in the future. “The study, however, did not see human perception of the species, which may also change. For example, it was predicted that some of the currently occupied suitable areas will be reduced in size, but what happens? it if the attitude of the people surrounding the area remains positive for the conservation of the species, then what would be the population of the golden langur,” Singha asked.Primatologist Dilip Chetry told Mongabay-India that the shrinking and habitat fragmentation are major known threats to the golden langur.” This article predicted how habitat shrinkage and fragmentation will pose a more serious threat to the golden langur in the near future. The document identified suitable habitats for future conservation initiatives. “However, the study did not provide impetus for analyzing the scope of restoring connectivity between suitable primary fragments to ensure the long-term conservation of the species. Some of the areas of occurrence shown on the map are outside the natural distribution of the golden langur. Additionally, the contraction range and areas of no change as shown on the map include areas beyond the range of the species,” Chetry said. “A study carried out two decades ago showed that the distribution of the golden langur in the forest of the Kakoijana reserve would only last for 60 years (study carried out on a particular model) but now the population there is increasing with the increase in green coverage thanks to the positive attitude of the people,” he said.

Community conservation is helping the species increase its population in some pockets of Assam. In Kakoijana Forest Reserve in Bongaigaon District, Assam, local communities involved in joint forest management committees in surrounding villages are contributing to the conservation of the species by protecting the forests. They have an intimate relationship with the forest. Recently, local communities living adjacent to the Kakoijana Reserve forest had objected to the Assam government’s decision to notify the area as a wildlife sanctuary as they believed that the demarcation of the protected area would bring violation of their rights. The community had said in the memorandum that their “dedication and sincere efforts have yielded positive results in restoring the forest canopy from less than 5% to over 70% and the golden langur population from less than 100 to almost 600 now in more than two decades.” A total of 34 villages with a population of about 2000 people are located adjacent to the reserve forest. “The situation may improve if the protected areas can be revitalized or protected with the active participation of the people,” Singha said. “Local communities are most helpful in this regard and have proven effective in many parts of Assam. However, their involvement in active conservation programs is vital. Sharma reiterated.

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  • The golden langur is in danger of extinction due to lack of suitable habitat
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