‘Spotlight on’

Western Hoolock Gibbon - Hoolock hoolock

Photographed 4th May 2009 by Stijn De Win.             Distribution of both Hoolock taxa with notes on the location of my sighting.   The Western Hoolock Gibbon (Hoolock Hoolock), now considered monotypic, was formerly lumped with Hoolock leucomedys, the Eastern Hoolock Gibbon.  The range boundary between the two former subspecies is formed by the Chindwin River with the Western Hoolock to occur in eastern Bangladesh, northeastern India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura), and northwestern Myanmar (west of the Chindwin River).  In India it is said to be restricted to points south of the Brahmaputra and east of the Dibang rivers.  Occurrence in China (extreme south-eastern Tibet) is not confirmed. Ok, so far the quick to read info bit –source IUCN red list. Continue reading;

Now, the animal photographed (and many more heard on the trip) lives in the Mishmi Hills in extreme NE India, in Arunachal Pradesh.  The area lies in the headwater region of the BrahmaputraRiver, which I would not exactly call “south of the Brahmaputra”.  Moreover, the area we visited in Mishmi Hills lies above the town of Roing where a road starts going up the mountains to the Mayodia pass and this area is not covered at all on both Western and Eastern Hoolock Gibbon distribution maps available on the IUCN website.  If you want to look this up, Roing lies about 1 cm to the right of the ‘h’ in Pradesh on these maps, at the foot of the hills. Western Hoolock range map ; http://www.iucnredlist.org/details/39876/0/rangemap Eastern Hoolock range map ; http://www.iucnredlist.org/details/39877/0/rangemap The dividing line in the range of both Hoolocks seems to be determined largely by major rivers.  There is no such river in between the Mishmi Hills above Roing and the population in China shown in the Western Hoolock distribution map.  Western Hoolock might therefore occur continuous and it would then be confirmed to occur in the south of this ‘range block’ at least…???

ID note Western Hoolock Gibbon males (as pictured) have eyebrows joined together and black underparts.  In the Eastern Hoolock Gibbon eyebrows are separated and the males show some pale brownish on the under parts.  Females of both species are brown.   Status The Western Hoolock Gibbon is listed as ‘endangered’ (Red List) and continues to decline.  There might be less than 300 left in Bangladesh with an estimated 2500 in India.  Surveys are needed in Myanmar as this country is likely to hold the largest and most viable populations. NamdaphaNational Park is considered ‘the’ stronghold of the species in India.   The Eastern Hoolock Gibbon is listed as ‘Vulnerable’ with a total population of in between 10,000 to 50,000 that mostly occur in Myanmar.   For both species, hunting and habitat loss are the main threats. Source IUCN red list

 

Western Hoolock are very shy animals and to make matters worse for the photographer, they live high up in the canopy of tall trees.  One can easily imagine how lucky I had been to make the ‘opening’ image in this article of a male high up in a tree that was positioned ‘down-slope’ so I could photograph it at eye level!  Perhaps it was too surprised I got it “In Focus” so quickly it could do nothing than pose and look into my lens!  He he and thank you.  I’ll try to bring you under the attention of the general public so they don’t forget to give these amazing animals the protection they deserve… The image left shows a more ‘conventional’ shot of the same male Hoolock.  Please note the fruits it was feeding on which are so important for these mammals being the main food source. photo by Stijn De Win

Ecology and Habitat Hoolock Gibbon inhabits mainly primary evergreen and some semi-evergreen forests where they are both arboreal and diurnal.  They occur in family groups of 3-6 individuals (Although the animal photographed seemed to be alone… –or others nearby went unnoticed?) We found our Gibbon in a fruiting tree and it’s no coincidence, as it is a frugivorous species.  Besides ripe fruits they feed also on leaves and buds with some animal matter such as insects taken occasionally. Source Mammals of South-east Asia, Charles M Francis   Voice Amazing!  It’s all I can say.  This is "the" sound of Asia (all Gibbon species) and unsurpassed by any bird song!  Listen and download!  Recording 1   -   recording 2  (Both recordings 6th May 2009, Mishmi Hills, by Stijn De Win.)

Hoolock Gibbon habitat in the Mishmi Hills, with the town of Roing visible at the edge of the Brahmaputra plains in the 3rd image.

Stijn De Win / Birding2asia.com published this information page on June 17th 2009.