Eastern Hoolock Gibbon (Hoolock leuconedys)


Hoolock Gibbons have experienced a drastic population decline in the past few decades. In the early 1970s the population in North-east India was estimated to be as many as 80,000 individuals, while currently there may be no more than 2,400.

Recent estimates for Bangladesh (200 to 280 individuals) and China (50 to 300) are no better.

Hoolocks are considered a priority for conservation in Myanmar. The immediate need was for a status review – critical for identifying, prioritizing, and planning conservation interventions to enhance options for the long-term survival of the Myanmar population of Hoolock Gibbons. We began this status review in 2008, under the collaborative Myanmar Primate Conservation Program.

Future hope for the Gibbons

Under this program, we reviewed all the available literature and many previously unpublished records for Hoolock Gibbons in Myanmar – and conducted extensive original research – to provide density estimates for both the Western and Eastern Hoolock Gibbon species in 25 locations.

Results confirm that by far the most significant populations of both species are in Myanmar, and this country therefore holds the global future of Hoolock Gibbons in its hands.

The immediate situation for Eastern Hoolock is relatively positive: large numbers are distributed across large areas of relatively intact forest. The situation for Western Hoolock is less promising: much of its former habitat is now degraded, but several larger blocks of suitable forest offer hope.

Indawgyi Lake Wildlife Sanctuary

Ample rice land and fisheries, and a limited tradition of hunting, mean direct threats to the species are low at this site. Easy access and potential for tourism combine to make it an ideal location for long-term protection and ecological research for the Eastern Hoolock Gibbon.

To reduce threats to habitat we are introducing supply- and demand-side interventions, including improved cooking methods and stoves, community forestry and village woodlots. To increase knowledge of the species we are introducing long-term research and monitoring.

All activities are being implemented in conjunction with the sanctuary management authority and local civil society groups, with the aim of building capacity for sustainable protection of the species.

Differences between the Western and Eastern Hoolock Gibbon

  • The two Hoolock species are separated by the Chindwin river in western Myanmar, which flows into the Irrawaddy.
  • The two forms differ in their fur coloration and DNA sequences, and may have diverged about 1.42 million years ago.
  • Sexes of both species have distinct white eyebrows. These are closer together in the Western Hoolock, making this the main visual diagnostic feature.