UPSC Prelims 2026 Q22: Western Hoolock Gibbon — Explained
With respect to the Western Hoolock Gibbons, which of the following statements is/are correct?
1. A Sanctuary in North-east India is home to this ape species listed as Endangered in the International Union for Conservation of Nature (IUCN) Red List.
2. They have specialized brachiation and can easily swing between trees.
3. They possess a strong and heavy build like gorillas, yet are remarkably agile tree climbers.
- 1 only
- 1 and 2
- 2 and 3
- 3 only
Answer: (b) 1 and 2
Statement-wise explanation
- 1: correct — The Hollongapar (Hoollongapar) Gibbon Sanctuary in Jorhat district, Assam, was given its present name in 1997. It is the only protected area in India named after a gibbon and holds about 125 Western Hoolock Gibbons. The IUCN Red List (2019 assessment) lists Hoolock hoolock as Endangered. Gibbons have no tail, so they are apes, not monkeys.
- 2: correct — Brachiation means swinging from branch to branch using only the arms. It makes up about 70–80% of a hoolock's movement. Gibbons are built for it, with very long arms, hook-like hands and a ball-and-socket wrist joint. They rarely walk on the ground, and when they do they walk upright and clumsily.
- 3: incorrect — Gibbons are 'lesser apes': small, slender and light. A Western Hoolock male weighs about 7 kg and stands about 80 cm tall. Gorillas are the largest great apes, and males can weigh over 150 kg. Gibbons are agile because they are light, not in spite of being heavy, so the 'strong and heavy build like gorillas' part is wrong.
How to eliminate
Statement 3 is the easiest to judge from basic knowledge. Gibbons swing by their arms through the top of the forest, and an animal built like a gorilla could not do that. Once 3 is out, options (c) and (d) go. That leaves 1 only or 1 and 2. Statement 2 only describes what gibbons are known for, and 'swing between trees' is the textbook picture of a gibbon, so the pair 1 and 2 follows. You do not need to be sure of the exact IUCN category in Statement 1 to get the answer. Still, remember these three facts: Western Hoolock is Endangered, Eastern Hoolock is Vulnerable, and Hollongapar Gibbon Sanctuary is in Jorhat, Assam.
Know more
Hoolock gibbons are India's only apes. Apes have no tail, which separates them from monkeys. They come in two groups:
| Group | Members | Build | Main way of moving |
|---|---|---|---|
| Lesser apes (family Hylobatidae) | Gibbons, incl. hoolocks | Small, slender, about 5–15 kg | Brachiation (arm-swinging) |
| Great apes (family Hominidae) | Orangutan, gorilla, chimpanzee, bonobo, humans | Large and heavy | Knuckle-walking or climbing; humans walk on two legs |
The three hoolock species
| Species | Where | IUCN status |
|---|---|---|
| Western Hoolock (Hoolock hoolock) | North-east India, Bangladesh, north-west Myanmar | Endangered |
| Eastern Hoolock (H. leuconedys) | Eastern Arunachal Pradesh, Myanmar, China | Vulnerable |
| Skywalker Hoolock (H. tianxing) | South-west China, Myanmar | Endangered |
Features worth remembering
- Males are black with a white brow; adult females are buff to tan.
- They live in small family groups of a pair and their young. They eat mostly fruit and spend nearly all their time in the canopy.
- Every morning they sing loud duets to mark their territory.
- Indian hoolocks are in Schedule I of the Wild Life (Protection) Act, 1972, the highest level of protection.
Hollongapar Gibbon Sanctuary (Jorhat, Assam)
- About 21 sq km of forest, cut off from other forest by tea gardens and villages. It was given its present name in 1997.
- It holds about 125 western hoolocks. Its other primates include the Bengal slow loris, the only nocturnal primate in north-east India.
- The Lumding–Dibrugarh railway runs 1.65 km through the sanctuary and splits it into two parts. In October 2024 the National Board for Wildlife approved electrifying this stretch. Railways have put up canopy bridges so gibbons can cross above the line.
Main threats: loss and break-up of forest, hunting, and roads, railways and power lines that cut through the canopy.
In the news
On 8 February 2026, a male Western Hoolock Gibbon was electrocuted on the newly electrified railway line inside Hollongapar Gibbon Sanctuary. It was the first such death, and it led to calls to reroute the line. A few months later, a gibbon was recorded crossing the railway on one of the canopy bridges. Both events kept the species and the sanctuary in the news in the run-up to Prelims 2026.
NCERT Concepts to Revise
- IUCN Red List: Statement 1 depends on the category the IUCN Red List's 2019 assessment gives Hoolock hoolock, so you need to know how the Red List ranks species.
- IUCN: Statement 1 names the International Union for Conservation of Nature, the global body whose assessments decide the conservation status of apes like the Western Hoolock Gibbon.
- Threatened species: Statement 1 needs you to know that 'Endangered' is one of the IUCN's threatened categories, which is why the Hollongapar Gibbon Sanctuary's protection matters.