Installation of artificial canopy bridges along State Highway-14 in Kokrajhar district has significantly reduced road accidents–related deaths of the endangered golden langur, according to a recent scientific study.

What is the issue?

• Golden Langur (Trachypithecus geei) is an Old World monkey.
• Roads and power lines fragment forest canopies, forcing langurs to descend to the ground, increasing the risk of vehicle collisions.
• A study in the Chakrashila–Amguri–Buxamara–Nayekgaon forest complex recorded:
  • 18 langur–vehicle collisions
  • 7 deaths, 5 major injuries, and 6 minor injuries
  • On a 5.2-kilometre stretch between Nayekgaon and Choibari on State Highway-14.

What solution was adopted?

• 15 artificial canopy bridges of four different designs were installed at 18 critical crossing points.
• Bridges were placed 9–10 metres above ground to mimic natural canopy height.
• Camera traps were used to monitor langur movement and bridge usage.

Key findings of the study

• 112 recorded crossings by eight golden langur groups.
• Langurs used canopy bridges far more than roads.
• Pipe and ladder-type bridges were the most effective designs.
• Before installation:
  • 71 per cent crossings were on the ground
  • 29 per cent used natural canopy
• After installation:
  • Ground crossings dropped sharply, reducing collision risk.

About Golden Langur

• The Golden Langur (Trachypithecus geei) is an endangered, arboreal primate known for its distinctive golden-orange fur.
• It is one of the most range-restricted primates in South Asia.
• They inhabit a restricted area bordered by the foothills of Bhutan (north), the Manas River (east), the Sankosh River (west), and the Brahmaputra River (south).

Geographical distribution

• Found only in a small transboundary region:
  • Western Assam (India)
  • South-central Bhutan
• In Assam, it mainly inhabits:
  • Kokrajhar
  • Bongaigaon
  • Chirang and adjoining forest areas
• A key habitat is the Chakrashila Wildlife Sanctuary, India’s first sanctuary declared specifically to protect the golden langur.

Habitat and behaviour

• They mostly occupy subtropical and temperate broadleaf forests at elevations from near sea level to above 3,000 metres.
• Strictly canopy-dwelling (arboreal) and rarely comes to the ground.
• Lives in groups, they are primarily herbivores, feeding mainly on:
  • Leaves
  • Fruits
  • Flowers
• Plays an important role in seed dispersal, helping forest regeneration.

Conservation status

• Listed as Endangered on the International Union for Conservation of Nature Red List and are placed under Appendix I of CITES.
• Protected under Schedule I of the Wildlife Protection Act, 1972.

Major threats

• Habitat loss and fragmentation due to:
  • Deforestation
  • Agriculture and settlements
  • Roads and power lines
• Road accidents and electrocution, especially where forest canopies are broken.
• Small and isolated populations reduce long-term survival chances.

Beyond bridges: community and policy role

• Some power lines were insulated to act as additional crossing pathways.
• The project includes:
  • Community awareness programmes
  • Incentives for restoring forest corridors through plantations
• Demonstrates how low-cost, science-based interventions can save endangered species.

Key terms explained

• Canopy bridge: Artificial structure that reconnects forest canopies across roads.
• Habitat fragmentation: Breaking of continuous habitat into isolated patches.
• Arboreal species: Animals that live mainly in trees.
• Anthropogenic mortality: Death caused by human activities.
• Wildlife corridor: Natural or artificial path that allows animal movement.

Exam Hook

Prelims – Statement-based Question

With reference to the golden langur, consider the following statements:

1. It is an arboreal primate endemic to the Indo-Bhutan region.
2. Habitat fragmentation forces it to descend to the ground, increasing road-kill risk.
3. Artificial canopy bridges increase vehicle speed in forest stretches.

Which of the statements given above is/are correct?

Answer: 1 and 2 only

One-line wrap:
Canopy bridges show how small design changes in infrastructure can make a big difference for wildlife conservation.