Context:

The Northeast Frontier Railway (NFR) has allocated funds to construct a canopy bridge for Hoolock Gibbon in Assam’s Hollongapar Gibbon Sanctuary.

More on the news

• This initiative aims to facilitate safe movement for the Hoolock Gibbon, across a railway track that divides its primary habitat in eastern Assam.
• The decision was made in consultation with the Assam State Forest Department, Wildlife Institute of India (WII), and other stakeholders.
• A 1.65-km-long track – set to be doubled and electrified – divides the 2,098.62-hectare Hollongapar Gibbon Sanctuary in the Jorhat district.
• The sanctuary has the largest concentration of the hoolock gibbon, one of 20 species of apes on Earth.
• The canopy bridges inside the sanctuary facilitate the movement of the gibbons across the track

The Hollongapar Gibbon Sanctuary

• It was renamed on 25 May 2004, formerly known as the Gibbon Wildlife Sanctuary or Hollongapar Reserve Forest, and is an isolated protected area of evergreen forest located in the Jorhat district of Assam, India.
• It was officially established and renamed in 1997.

About Hollock Gibbon 

• They are the only ape found in India.
• They are known for their vocalisation, and spend much of their time on the upper canopy of tall trees, mostly the hollong (Dipterocarpus macrocarpus).

In 2005, the western and the eastern hoolock gibbons were classified as two distinct species.

• Western Hoolock Gibbon: also known as white-browed gibbons. They thrive in the dense forests that extend from east of the Brahmaputra River in northeast India, through Bangladesh, and into western Myanmar.
• Eastern Hoolock Gibbon: It is Endemic to Myanmar. They live in the forests between the Chindwin and Irrawaddy rivers that flow through the northern half of Myanmar. It inhabits specific pockets of Arunachal Pradesh and Assam in India.

Of the two, the western hoolock is listed as Endangered in the IUCN Red List, while the eastern hoolock is listed as Vulnerable, and both species are listed on Schedule 1 of the Indian Wildlife Protection Act 1972. 

• Adults exhibit distinct sexual dimorphism in pelage coloration, the males are black overall and the females become varying shades of brown and fawn at maturity.

Behaviour: 

• Gibbons are primarily monogamous, forming long-lasting pair-bonds, and are typically found in small family groups with a single adult female, a single adult male and one to four offspring.

Habitat: 

• The species inhabits mature forests; tropical evergreen forests, wetter tropical semi-evergreen forests, sub-tropical monsoon evergreen broadleaf forests, and sub-tropical evergreen broadleaf hill or mountain forests. 
• They are less commonly found in deciduous and scrub forests and are absent from mangroves.
• Their home ranges can extend to woodlands or orchards, particularly in regions surrounding Nokrek National Park in Meghalaya and the Barikuri area in Tinsukia district, Assam. 
• Similar habitat patterns are observed in the southeastern boundaries of Mehao Wildlife Sanctuary in Arunachal Pradesh.