Primatologists have proposed a solution to address the division caused by a 1.65-km long railway track within the Hollongapar Gibbon Sanctuary in eastern Assam, dedicated to the western hoolock gibbon.
- The sanctuary, home to about 125 hoolock gibbons, is facing habitat fragmentation due to the track’s presence, which has separated gibbon populations on either side.
- To counter this, scientists from the Wildlife Institute of India (WII) have suggested constructing an artificial canopy bridge to enable the gibbons to move across the railway line.
- This would help maintain genetic diversity and support the survival of the endangered gibbons, which are highly sensitive to disruptions in their canopy habitat.
Location and Geography
- Hollongapar Gibbon Sanctuary was established in 1997 primarily for the conservation of the Hoolock Gibbon and its habitat.
- Hollongapar Gibbon Sanctuary is situated in the Jorhat district of Assam, near the town of Mariani.
- It covers an area of approximately 20.98 square kilometres (8.11 square miles).
- The sanctuary is characterized by semi-evergreen and mixed deciduous forests, offering a diverse range of habitats for various flora and fauna.
Biodiversity
- The sanctuary is renowned for its role in the conservation of the Western Hoolock Gibbon (Hoolock hoolock), which is listed as Endangered on the IUCN Red List.
- Apart from gibbons, the sanctuary is home to various other primate species, including the Stump-tailed Macaque and Capped Langur.
- The avian diversity is also significant, with a variety of bird species such as the Great Hornbill, Green Imperial Pigeon, and White-cheeked Partridge.
Vegetation
- The sanctuary’s vegetation includes semi-evergreen and mixed deciduous forests, with a range of tree species like Holong (Dipterocarpus macrocarpus) from which the sanctuary gets its name.
- The diverse forest types provide important habitats for the resident and migratory species.
About Western Hoolock Gibbon
- Hoolock hoolock is a primate species belonging to the family Hylobatidae, commonly known as gibbons.
- They are found in parts of South Asia, primarily in India, Bangladesh, and Myanmar.
- The estimated current population of hoolock gibbons is around 12,000 individuals.
Taxonomy and Classification
- The Western Hoolock Gibbon is one of the two species of hoolock gibbons, the other being the Eastern Hoolock Gibbon (Hoolock leuconedys).
- Hoolock gibbons are small apes and are often referred to as “lesser apes,” in contrast to the larger “great apes” like chimpanzees, gorillas, orangutans, and humans.
Physical Characteristics
- Western Hoolock Gibbons have a distinct appearance with a black or dark brown fur coat, with a white face ring and pronounced eyebrows.
- Males and females have similar appearances, but males are slightly larger than females.
- They have long arms, which are well adapted for brachiation (swinging from branch to branch) through the trees.
Habitat
- Western Hoolock Gibbons are found in a variety of forest types including tropical rainforests, subtropical forests, and mixed deciduous forests.
- They inhabit the upper canopy layers of trees and are highly arboreal, rarely descending to the ground.
Geographical Distribution
- The Western Hoolock Gibbon’s range extends across parts of northeastern India, northern and western Myanmar (Burma), and southwestern China.
- In India, their distribution spans states like Assam, Arunachal Pradesh, and Nagaland.
Behaviour and Ecology
- Gibbons are known for their impressive vocalizations, which play a crucial role in marking territory and maintaining group cohesion. They are known to produce songs that can be heard over long distances.
- These gibbons are primarily frugivorous, feeding on a variety of fruits, leaves, and occasionally insects.
- They live in small family groups consisting of a monogamous pair (male and female) and their offspring. These groups usually consist of two to four individuals.
- Their social structure revolves around strong pair bonds between males and females, who often perform duets as part of their territorial behaviour.
Conservation Status
- The Western Hoolock Gibbon is listed as Endangered on the International Union for Conservation of Nature’s (IUCN) Red List.
- The Eastern Hoolock Gibbon is listed as Vulnerable on the IUCN Red List.
- Both species are listed on Schedule 1 of the Indian (Wildlife) Protection Act 1972, which offers them the highest level of legal protection in India.
International Union for Conservation of Nature’s Red List: - Western Hoolock Gibbon: Endangered
- Eastern Hoolock Gibbon: Vulnerable.
- Schedule 1 of the Indian (Wildlife) Protection Act 1972.