UPSC Prelims 2026Question 22Environment

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.
Select the answer using the code given below:

Options

(a)1 only
(b)1 and 2
(c)2 and 3
(d)3 only

Correct answer: b

Decision rule

Body plans must match locomotion: a brachiating ape is light with long arms, so borrowing a gorilla's heavy build makes the statement false.

Explanation

Correct Answer

(b) 1 and 2

Explanation of the Correct Answer

Statements 1 and 2 are correct, while statement 3 is incorrect.

Statement 1 is correct:
The Western Hoolock Gibbon is found in North-east India. Hoollongapar Gibbon Wildlife Sanctuary in Assam is especially associated with this species. The Western Hoolock Gibbon is listed as Endangered on the International Union for Conservation of Nature (IUCN) Red List.
Statement 2 is correct:
Western Hoolock Gibbons are highly arboreal apes. They move through the forest canopy using brachiation, a specialized mode of locomotion in which they swing from branch to branch using their long arms. WWF-India notes that hoolock gibbons swing from tree to tree through brachiation and can cover large distances in a single swing. (WWF India)
Statement 3 is incorrect:
Western Hoolock Gibbons do not possess a strong and heavy build like gorillas. They are relatively small, slender-bodied apes with long arms adapted for arboreal life. Their agility comes from their light body and long arms, not from a gorilla-like build.

Therefore, the correct answer is (b) 1 and 2.

Why Other Options Are Incorrect

Option	Verdict	Explanation
(a) 1 only	Incorrect	Statement 1 is correct, but statement 2 is also correct because Western Hoolock Gibbons are specialized for brachiation.
(b) 1 and 2	Correct	They are Endangered apes found in North-east India, and they move by brachiation.
(c) 2 and 3	Incorrect	Statement 2 is correct, but statement 3 is incorrect because they are not heavily built like gorillas.
(d) 3 only	Incorrect	Statement 3 is incorrect.

Relevant Supplementary Information

Western Hoolock Gibbon: Key Facts

Aspect	Details
Scientific name	Hoolock hoolock
Common name	Western Hoolock Gibbon
Taxonomic group	Ape
Distribution in India	North-east India, especially Assam and adjoining states
Important sanctuary	Hoollongapar Gibbon Wildlife Sanctuary, Assam
IUCN status	Endangered
Habitat	Tropical and semi-evergreen forests
Locomotion	Brachiation
Body type	Slender body, long arms, adapted for canopy movement
Major threats	Habitat loss, fragmentation, railway lines, hunting and human disturbance

Statements and Their Verification

Statement	Correct / Incorrect	Reason
1. A Sanctuary in North-east India is home to this ape species listed as Endangered in the IUCN Red List.	Correct	Hoollongapar Gibbon Wildlife Sanctuary in Assam is home to hoolock gibbons; Western Hoolock Gibbon is Endangered.
2. They have specialized brachiation and can easily swing between trees.	Correct	Their long arms and arboreal lifestyle make them highly adapted for swinging between trees.
3. They possess a strong and heavy build like gorillas, yet are remarkably agile tree climbers.	Incorrect	They are not gorilla-like or heavily built; they are slender, lightweight canopy specialists.

Gibbons vs Gorillas

Feature	Western Hoolock Gibbon	Gorilla
Body size	Small ape	Largest living ape
Build	Slender and lightweight	Heavy and powerful
Arms	Very long, suited for swinging	Strong, suited for knuckle-walking and climbing
Primary locomotion	Brachiation	Knuckle-walking and climbing
Habitat use	Mostly arboreal	Mostly terrestrial, though can climb
Indian distribution	Found in North-east India	Not found in India
Conservation issue in India	Habitat fragmentation and canopy breaks	Not applicable

Key Takeaways from the Tables

Western Hoolock Gibbon = India’s only ape species.
It is found in North-east India, especially associated with Hoollongapar Gibbon Wildlife Sanctuary, Assam.
It is listed as Endangered on the IUCN Red List.
It moves through trees by brachiation.
It is not heavily built like a gorilla; it is a slender, long-armed canopy specialist.

Point	Explanation
Western Hoolock Gibbon = India’s only ape	This is a major prelims-relevant fact.
Found in North-east India	Especially associated with Assam and adjoining North-eastern forests.
Hoollongapar Gibbon Wildlife Sanctuary is key	It is a major protected area for this species.
IUCN status = Endangered	Western Hoolock Gibbon faces a high risk of extinction in the wild.
Brachiation is the key adaptation	Long arms help it swing between trees.
Not gorilla-like	It is slender and arboreal, not heavy-bodied.
Canopy connectivity is crucial	Forest fragmentation is a serious threat to its survival.

Context and Current Relevance

Hoolock gibbons are important indicators of healthy forest canopy ecosystems in North-east India.
Habitat fragmentation is a serious threat because gibbons depend on continuous tree cover for movement.
Recent conservation efforts in Assam include canopy bridges to help gibbons cross fragmented habitats safely.

Table: Western Hoolock Gibbon at a Glance

Aspect	Details
Common name	Western Hoolock Gibbon
Scientific name	Hoolock hoolock
Animal group	Ape
Special importance	India’s only ape species
Distribution in India	North-east India
Important habitat	Hoollongapar Gibbon Wildlife Sanctuary, Assam
IUCN Red List status	Endangered
Habitat type	Tropical, semi-evergreen and evergreen forests
Movement	Brachiation
Body structure	Slender body, long arms, lightweight build
Major threats	Habitat loss, forest fragmentation, canopy breaks, hunting and human disturbance

Table: Hoolock Gibbons in India

Species	Scientific Name	Distribution in India	Conservation Status	Important Point
Western Hoolock Gibbon	Hoolock hoolock	Assam, Meghalaya, parts of Arunachal Pradesh and other North-eastern areas	Endangered	More widely known Indian hoolock gibbon species
Eastern Hoolock Gibbon	Hoolock leuconedys	Parts of Arunachal Pradesh and North-east India	Vulnerable / threatened	More restricted distribution in India

Table: Gibbons vs Other Apes

Feature	Western Hoolock Gibbon	Gorilla	Chimpanzee / Orangutan
Body size	Small ape	Largest ape	Medium to large apes
Build	Slender and lightweight	Heavy and muscular	Strong but varies by species
Main movement	Brachiation	Knuckle-walking and climbing	Climbing, walking and swinging
Arm structure	Very long arms	Strong arms, not specialized for brachiation like gibbons	Long arms, especially in orangutans
Habitat use	Mostly arboreal	Mostly terrestrial	Arboreal and terrestrial depending on species
Presence in India	Found in North-east India	Not found in India	Not found in India
Key adaptation	Swinging through forest canopy	Strength and ground movement	Climbing and tool/social behaviour depending on species

Table: Important Terms Related to Gibbons

Term	Meaning	Relevance to Western Hoolock Gibbon
Brachiation	Movement by swinging from branch to branch using arms	Main locomotion of gibbons
Arboreal	Tree-dwelling	Hoolock gibbons live mostly in trees
Canopy	Upper layer of forest formed by tree crowns	Gibbons depend on continuous canopy cover
Ape	Primate without a tail	Hoolock gibbons are apes, not monkeys
Primate	Mammalian order including monkeys, apes and humans	Gibbons belong to this group
Endangered	IUCN category indicating high risk of extinction in the wild	Western Hoolock Gibbon is listed as Endangered
Habitat fragmentation	Breaking of continuous habitat into smaller patches	Major threat because gibbons need connected tree cover

Table: Important Wildlife Areas Associated with Gibbons

Protected Area / Region	State	Importance
Hoollongapar Gibbon Wildlife Sanctuary	Assam	India’s only sanctuary named after gibbons; key habitat for Western Hoolock Gibbon
Dihing Patkai National Park	Assam	Important rainforest habitat in Upper Assam
Namdapha National Park	Arunachal Pradesh	Rich biodiversity area; associated with several primates
Mehao Wildlife Sanctuary	Arunachal Pradesh	Important North-east forest habitat
Nokrek Biosphere Reserve	Meghalaya	Important forest and biodiversity landscape
Barail Wildlife Sanctuary	Assam	Forested landscape supporting primates and other fauna

Table: Common Confusions Related to Hoolock Gibbons

Confusion	Correct Understanding
Gibbons are monkeys	Incorrect. Gibbons are apes, and apes do not have tails.
Western Hoolock Gibbons are heavily built like gorillas	Incorrect. They are slender, lightweight and long-armed.
Gibbons mainly walk on the ground	Incorrect. They are mostly arboreal and move through brachiation.
Western Hoolock Gibbon is found all over India	Incorrect. It is restricted mainly to North-east India.
Hoollongapar Gibbon Sanctuary is in Arunachal Pradesh	Incorrect. It is in Assam.
Brachiation means jumping on the ground	Incorrect. It means swinging between trees using arms.
Habitat fragmentation does not affect gibbons much	Incorrect. It severely affects them because they require connected tree canopies.

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