A stranded family of Hoolock gibbons was recently rescued after a challenging four-day operation in Arunachal Pradesh’s Lower Dibang Valley, drawing attention to the conservation needs of India’s only ape species.
Basics about Hoolock Gibbons
The Hoolock gibbon is one of the 20 gibbon species globally and is recognised as the only ape species found in India, making it evolutionarily significant as apes are closest to humans.
It is also called the White-Browed Gibbon and bears the scientific name Bunopithecus hoolock.
As smallest and fastest apes, they move through forests using a specialised locomotion technique known as brachiation, which allows them to swing rapidly between trees.
Distribution and Habitat
The species is widely distributed across Northeast India, Bangladesh, Myanmar, and southern China, making it a transboundary conservation species.
In India, it is strictly located south of the Brahmaputra River, inhabiting states such as Assam, Meghalaya, Arunachal Pradesh, Nagaland, Mizoram, Manipur, and Tripura.
Hollongapar Gibbon Sanctuary in Assam hosts the largest known population of Hoolock gibbons in the country.
Two recognised species occur in India:
Eastern Hoolock Gibbon (Hoolock leuconedys) – confined to a specific range in Arunachal Pradesh.
Western Hoolock Gibbon (Hoolock hoolock) – widespread across other northeastern states.
They prefer tropical semi-deciduous and deciduous forests, especially three-tiered canopies that provide food, shelter, and structural support for arboreal movement.
Key Characteristics and Behaviour
Hoolock gibbons are diurnal and fully arboreal, spending almost all their time in tree canopies.
They are monogamous, forming long-term pair bonds and living in small family units.
Their communication includes complex, territorial duet songs performed by males and females.
They show sexual dichromatism, with males displaying black coats and white eyebrows, while females have golden-brown or buff coloration.
Adult body size ranges from 45.7–63 cm, with weight between 6–8 kg, making them relatively lightweight but agile apes.
As keystone species, they support ecosystem health by aiding seed dispersal and maintaining forest diversity.
Diet and Ecological Role
They are primarily frugivorous, feeding on fruits but also consuming leaves, flowers, buds, and occasional insects.
Their diet helps them perform a crucial ecological function as seed dispersers, which sustains forest regeneration and biodiversity.
Conservation Status and Threats
IUCN Red List Status:
Eastern Hoolock Gibbon – Vulnerable
Western Hoolock Gibbon – Endangered
Both species are listed under Schedule I of the Wildlife (Protection) Act, 1972, providing them the highest level of legal protection.
Major threats include:
Habitat fragmentation caused by deforestation, road building, and expansion of settlements.
Shifting cultivation (jhuming), which breaks canopy continuity essential for their movement.
Poaching for meat and supposed medicinal uses.
Infrastructure projects, including dams and transmission lines, which isolate populations.
Conservation efforts require maintaining canopy connectivity, strengthening anti-poaching mechanisms, and involving local communities.
