A female hoolock gibbon photographed in the Hoollongapar Gibbon Sanctuary. Image by Miraj Hussain via Wikimedia Commons (CC BY-SA 4.0).

There is only one type of ape in India, the hoolock gibbon. Several families of hoolock gibbons live in Hoollongapar Gibbon Sanctuary in India’s northeastern state of Assam.

The gibbon sanctuary has been divided by a railroad for many decades, and the gibbons have not crossed over the tracks. This is because Hoolock gibbons are tree-living (arboreal) and don’t like to come to the ground.

People built a bridge for the gibbons to cross the tracks, but the gibbons were never seen using it.

A bridge built over the tracks in 2015 with funds from the railway department. Since the bridge does not connect to the forest canopy, gibbons have not been observed using it to cross the tracks. Image by Anuraag Baruah.

People started planting trees along the tracks in the early 2000s. Now there is a canopy of trees crossing the railroad tracks. And for the first time a family of gibbons was observed crossing it.

This is important for the gibbons in the sanctuary because it means that the families of gibbons that have been separated from each other for decades can now access each other and use forest on both sides of the railroad.

Good news for hoolock gibbons!

Watch this video to see how the gibbons use the tree canopy to cross the tracks:

This video has English subtitles. Gibbons seen crossing the canopy at 2:14 and 2:27.

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