Species File: Exploring India’s biodiversity, one species at a time.
In the forests of northeast India, a series of whoops and hoots rises through the canopy in a melodious crescendo every morning — the unmistakable song of the western hoolock gibbon. Pairs often duet to mark their territory, reinforce pair bonds and communicate with their family members.
The western hoolock gibbon (Hoolock hoolock) is India’s only ape. While adult males have a fully black coat, females are buff to golden-brown. Exclusively arboreal, which means they spend their lives on trees, they use their long arms to swing between branches with ease. They feed primarily on fruits, and occasionally leaves and insects, making them vital for seed dispersal and forest regeneration.
In India, the species is found in the tropical and subtropical forests of the northeast, across Assam, Arunachal Pradesh, Meghalaya, Manipur, Mizoram, Nagaland, and Tripura, with populations extending into Bangladesh, Myanmar, and perhaps southern Tibet. Two other hoolock gibbon species — the eastern hoolock gibbon (Hoolock leuconedys) and the Gaoligong hoolock gibbon (Hoolock tianxing) — are found in Myanmar and China.
An estimated 90% of the global hoolock gibbon population has been lost over the past three decades. Around 3,000 western hoolock gibbons are believed to remain; 2,600 of them in India. According to the IUCN Red List, the western hoolock gibbon is listed as endangered, as is the Gaoligong hoolock gibbon; the eastern hoolock gibbon is listed as vulnerable. The species receives the highest level of legal protection in India, under Schedule I of the Wildlife (Protection) Act, 1972.
Hoolock gibbons require contiguous, closed-canopy forests for survival, and are thus highly vulnerable to habitat loss and fragmentation. The loss of even a single connecting tree can render fragments unreachable. Hunting and the illegal pet trade compound the pressure.
In an earlier story published by Mongabay-India in 2019, primatologist Narayan Sharma, Cotton University, Assam, said: “When a contiguous habitat is reduced to scattered smaller fragments, they become ‘habitat islands’ in an inhospitable sea of degraded habitat. This could result in inbreeding. The resultant offspring are often weak, sometimes sterile or may have little reproductive fitness.”
Read more about the hoolock gibbon in our stories on saving India’s only ape, community conservation efforts, and how tree bridges could help connect fragments.
Banner image: A western hoolock gibbon in Namdapha Tiger Reserve. While adult males have a fully black coat, females are buff to golden-brown. Image by Rohit Naniwadekar via Wikimedia Commons (CC BY-SA 4.0).
Credits
