Why in News

• Canopy bridges of planted trees and gantry bridges are helping hoolock gibbons cross railway lines in Assam. Road and rail lines have split their forest habitat, and the western and eastern hoolock populations have fallen by about 90% in recent decades.

Key Facts — About the hoolock gibbon

• It is India’s only ape and lives in Northeast India, mostly south of the Brahmaputra.
• Adults are about 3 feet tall with 5-foot arms.
• They live in trees and need a continuous canopy, and they are easy prey for wild dogs and leopards on land.
• They mate for life and guard their territory, so small isolated groups suffer from inbreeding and decline.
• The western hoolock gibbon is Endangered and the eastern hoolock gibbon is Vulnerable on the IUCN Red List. Both are in Schedule I of the Wildlife (Protection) Act, 1972.

About other species and examples

• The lion-tailed macaque near Valparai (Tamil Nadu) faces habitat fragmentation by tea and coffee estates and roads.
• Rope bridges help the giant Indian squirrel at the Melghat Tiger Reserve and the Srivilliputhur Grizzled Squirrel Sanctuary.
• The Netherlands has an animal overpass nearly 1 km long, which spans a highway, a rail yard and a golf course.