EPOW - Ecology Picture of the Week

Gibbon in Peril

Western Hoolock Gibbon (Hoolock hoolock), Family Hylobatidae
Garo Hills, Meghalaya, Northeast India

Explanation:  Warily eyeing us from his bamboo and evergreen forest copse of northeast India is this striking male hoolock gibbon.  

The female mate and young of this pair were presented in a previous EPOW episode.  

Gibbons are masters of brachiation, that is, locomotion through the forest canopy by means of swinging by their arms.  

Their arms are so well adapted for this motion that they can swiftly move through the forest canopy with very little energetic cost. 

Male hoolocks are notable for their white eyebrows and black fur.  

A recent evaluation by the IUCN Primate Specialist Group suggests that hoolock gibbons are in peril and qualify as one of the 25 most endangered primates on the planet.  

Their populations are declining from habitat disruption, and some of their populations are small and isolated enough to "wink out" from just random chance.    

Other lesser, but still additive, threats include poaching and continued fragmentation and isolation of their forest environment from clearing for slash-and-burn agriculture.

 
What will be the future for this amazing great ape?
Hoolocks are important dispersal agents of plant seeds
in their tropical evergreen forests, and thus they play a key
ecological role in forest health and diversity.
When they disappear, how might the forest suffer?

A note on hoolock taxonomy:  Intrepid Indian trekker, master photographer, and wildlife biologist Tom Kogut reminded me that recently the species has been split.  

Western Hoolock Gibbon (Hoolock hoolock), featured here, has been divided from what is now called Eastern Hoolock Gibbon (Hoolock leuconedys).  The former is highly endangered, as noted by IUCN (see link in the above text).  

I had visited several of the forest habitat fragments in Meghalaya, northeast India, where the Western Hoolock Gibbon still resided as isolated, tiny colonies or individual family units.  For how long, though, is uncertain.  

Information:
     Kakati, K.  2006.  Fragment-living, a study of hoolock gibbons in Assam, India.  Gibbon's Voice 8(1):451-464.
     Vereecke, MF, K D'Aout, and P Aerts.  2009.  Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle.  J. Anatomy 215(3):335-354.