A stretch of the rail track that cuts through the gibbon sanctuary

Guwahati, Jan. 3: A tribe of gibbons that was split into two by a rail track passing through their habitat is to be reunited after several decades of separation by two steel bridges designed to look like trees.

Northeast Frontier Railway has decided to build the two bridges over an 800-metre stretch of the Gibbon Wildlife Sanctuary in Jorhat district of Assam to compensate for the forced separation of the two groups.

Gibbons are an exclusively arboreal (tree-dwellers) species and do not set foot on the ground. When laying the rail track in the thirties, nobody in the railways or the forest department possibly realised that the gibbon population would be bifurcated along with the stretches of forest on either side.

Rajveer Singh, an assistant executive engineer in NF Railway’s Mariani division, said the two steel bridges would be camouflaged to look like trees with branches and encourage the gibbon population on either side of the track to mingle.

The sanctuary, located near Mariani along the Assam-Nagaland border, has 21 gibbon families with an average of four members in each. Gibbons are an endangered species and listed in Schedule I of the Wildlife Protection Act, 1972. Apart from the northeastern states, they are found in Bangladesh, Myanmar and the southern parts of China.

Singh said the twin bridges would be the first of their kind in the country. “We have identified the sites and will submit a project proposal to the forest department for clearance very soon. Work will start as soon as the forest department pays the deposit fund.”

On December 18, a team of railway and forest officials surveyed a portion of the track across which the “gibbon bridges” are to be built.

The divisional forest officer of Jorhat, R.K. Das, said it was the forest department that came up with the idea of building two bridges to restore the “gene flow” between gibbon families in the 20.98-square km sanctuary.

Das said it was not known how many gibbons the sanctuary had lost because of the track. “Conservation efforts gained momentum only after the forest was declared a sanctuary in 1979.”

The sanctuary was previously known as the Hollongapar reserve forest.

Assistant conservator of forests Gunin Saikia said the gibbon families living on either side of the track had not increased in size because there were not enough males. Gibbons are known to be monogamous.

The gibbon sanctuary is also home to six other species of primates — capped langur, pig-tailed macaque, stump-tailed macaque, Assamese macaque, rhesus macaque and slow loris — besides leopards, pythons and elephant herds.