Canopy Bridges for Gibbons in Assam

Table of Contents

Context: The Northeast Frontier Railway (NFR) has allocated funds to build canopy bridges over a railway track that splits the primary habitat of India’s only ape species in eastern Assam.

Canopy Bridges

A canopy bridge is a type of wildlife crossing that is specifically designed for arboreal (tree-dwelling) species.
These bridges are constructed above the ground, usually connecting fragmented patches of forest that have been divided by roads, railways, or other human constructions.

Key Features and Benefits of Canopy Bridges

Habitat Connectivity: Canopy bridges are crucial for restoring and maintaining habitat connectivity in fragmented landscapes.
- They allow animals to move freely between different areas of their habitat, which is vital for accessing resources, finding mates, and maintaining healthy populations.
Reduction in Wildlife Mortality: By providing a safe route over dangerous obstacles like roads and railway tracks, canopy bridges help reduce the risk of wildlife-vehicle collisions, which are a significant threat to many species.
Genetic Diversity: The bridges facilitate gene flow between isolated populations, which is essential for preventing inbreeding and ensuring long-term genetic diversity, crucial for the species’ resilience to environmental changes.
Design and Implementation: The construction of canopy bridges can be adapted to various environments and budgets, ranging from simple rope bridges to more sophisticated structures that mimic natural forest canopies.

About Hoolock Gibbon

Hoolock Gibbons, renowned for being the smallest and swiftest apes, reside in the tropical and subtropical forests of Southeast Asia.
They are highly intelligent, exhibit unique personalities, and maintain strong familial ties, common traits in apes.
They are among the 20 species of gibbons globally and are the sole ape species found in India.
Characterised by their prominent white eyebrows, elongated arms, and a throat pouch used for vocalising.

Arboreal Lifestyle and Challenges
- Tree-Dwelling Habits: Gibbons are entirely tree-dwelling, spending their existence in the forest canopies.
- Sensitivity to Habitat Changes: They are acutely affected by disruptions in their habitat, such as breaks in the canopy.
- Risks of Habitat Fragmentation: Habitat division can cause genetic isolation and pose a risk to their populations.

Gibbon Varieties in India

Western Hoolock Gibbon (Hoolock hoolock)

Geographic Spread: Found across northeastern India, specifically south of the Brahmaputra River and east of the Dibang River, and also in eastern Bangladesh and northwest Myanmar.
Conservation Status: Classified as ‘Endangered’ on the IUCN Red List.

Eastern Hoolock Gibbon (Hoolock leuconedys)

Habitat: Inhabits areas in Arunachal Pradesh and Assam in India, and regions in southern China and northeast Myanmar.
Conservation Status: Listed as ‘Vulnerable’ on the IUCN Red List.

Note: Both species are protected under Schedule 1 of the Indian (Wildlife) Protection Act of 1972.

Gibbon Wildlife Sanctuary

Location: Nestled in the Jorhat district of Assam, India, lies the Hollongapar Gibbon Sanctuary (HGS), a haven for the endangered western hoolock gibbon.
Establishment and Geographical Area: Formerly known as the Gibbon Wildlife Sanctuary or Hollongapar Reserved Forest is an isolated protected area of evergreen forest.
- The sanctuary was officially constituted and renamed in 1997.
- This protected area encompasses approximately 20.98 square kilometres, safeguarding the sanctuary’s rich biodiversity.
Unique Inhabitants: The HGS not only harbours India’s only gibbons but also serves as home to Northeastern India’s sole nocturnal primate, the Bengal slow loris.