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Hoolock gibbon


CITES: Appendix I (What is CITES?)
IUCN Red List: H. hoolock: EN; H. leuconedys: VU (What is Red List?)
Key: EN = Endangered, VU = Vulnerable
(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

H. hoolock
Hoolock hoolock
Photo: Alan Mootnick

In general, hoolocks are extremely threatened with the western variety, H. hoolock listed as one of the World's 25 Most Endangered Primates, 2006-2008. It is said that the species' survival is entirely contingent on human action and their numbers, over 100,000 in the 1970's, have seen a dramatic reduction (Walker et al. 2007). Populations in Bangladesh number a combine total of around 200 individuals, and even these numbers are in very small and isolated populations with low long-term viability (Biswas et al. 2003; Molur et al. 2005; Walker et al. 2007). The total population in northeast India is between 1700 and 2200 individuals (Choudbury 2007). The best hope for the western hoolock gibbon is in Myanmar where there is around 50,000 km² of forest in the Rakhine Yoma region, with 175,500 ha managed by the Nature and Wildlife Conservation Division of the Forest Department of Myanmar (Walker et al. 2007). At present, it seems that the eastern hoolock gibbon situation in Myanmar is more secure based on preliminary surveys (Walker et al. 2007) with a rough estimate of 30,000 east of the Chindwin River (A Mootnick & W Brockelman pers comm.). However, in China, the numbers of eastern hoolocks are estimated at less than 150 individuals (Zhang 1998). All told, unless habitat loss is stopped, chances are high that the western hoolock will become extinct within 50 years (Walker 2005).

Hoolock gibbons are protected by law in India making it illegal to kill or capture the species, but their conservation has been less a priority than that for other large mammals in the nation (Molur et al. 2005; Choudhury 2006). In addition, a reliance on forest resources is exacerbated by human population pressure, immigration and bad economic conditions (Das 2002-2003; Walker et al. 2007). In fact, in some areas, everyone living in proximity to hoolock gibbon habitat is reliant on the forest for their livelihood (Mukherjee et al. 1988). Compounding the problem, authorities have little power to curtail illegal forest use (Srivastava et al. 2001). Essentially, hoolock gibbons are seriously threatened ultimately due to some of the highest human growth rates in the world which result in habitat degradation (Gupta et al. 2005).

The species are especially vulnerable to habitat degradation and destruction due to their preferences for pristine forests with contiguous canopy. As a result, they have a hard time living in secondary forests and discontinuity of forests is a major problem for the species (Mukherjee 1986; Mukherjee et al. 1991-1992; Kakati 2006; Osterberg 2007).


Threat: Human-Induced Habitat Loss and Degradation

As is the case with most primates, the primary threat to the hoolock is habitat destruction, degradation, and fragmentation (Das et al. 2003; Dam 2006). Reasons for habitat destruction and degradation include, but are not limited to, logging (both legal and illegal), bamboo harvesting for paper manufacture as well as for domestic uses, tree bark extraction, road construction, monoculture tree plantations, fuel wood extraction, coal mining, stone quarrying, livestock grazing, and agriculture, including tea and rice cultivation (Mootnick et al. 1987; Choudhury 1996; Ahsan 2001; Das 2002-2003; Das et al. 2003; Choudhury 2006; Kakati 2006; Osterberg 2007). While local-level timber extraction for fuel may not profoundly affect the forest, commercial-level extraction most assuredly does, resulting in profound forest degradation (Ahsan 2001). Other factors precipitating hoolock habitat destruction include the conversion of rainforest to plantations of teak, hydro-electric dam projects, high-tension electric wires, roads, railways, oil drilling, irrigation, and encroaching human settlement (Choudhury 1990; 1996; Dam 2002-2003; Das et al. 2006). Betel Leaf (a south Asian spice) cultivation also causes primates to become absent from potential habitat, with methods used in the growing of the plant rendering forests unsuitable for hoolock gibbons (Ahsan 2001). Shifting cultivation ("Jhum") is a common method of slash-and-burn agriculture in eastern India in which new fields are cleared each year, resulting in rapid deforestation (Mukherjee et al. 1992; Gupta 1994). It is agricultural methods of this type that are the primary reason for the fragmentation degradation, and clearing of hoolock habitat in some areas (Alfred & Sati 1990; Choudhury 1996).

Threat: Invasive Alien Species

Hoolock gibbons are occasionally killed by domestic dogs when they come to the ground to cross gaps in discontinuous degraded forest (Choudhury 2000).

Threat: Harvesting (hunting/gathering)

Hoolock gibbons are hunted for food by several ethnic groups in northeast India, utilizing snares, muzzle-loading and automatic firearms (Mukherjee et al. 1992; Choudhury 1990; 1991; 1996; 2006). Further, hunting and poaching by both local and non-local individuals are significant threats to populations (Mootnick et al. 1987; Choudhury 1991). Hoolock gibbons are also hunted for folk medicine (Walker et al. 2007). However, in some areas, such as parts of Arunachal Pradesh, India, hoolock gibbons are not hunted, often for religious reasons and in fact, sightings on the ground are sometimes considered to be bad omens (Choudhury 2000; Ahsan 2001). Gibbons are also sometimes hunted for commercial sale and hoolock meat has been found for sale in markets. Further, the species are sometimes taken for trade and sub-adults are sometimes taken as pets (Choudhury 2006; Walker et al. 2007).

Threat: Human Disturbance

Tourism has the potential to degrade hoolock gibbon habitat due to visitor littering, disturbance of the animals, and collateral pollution (Ahsan 2001). Also, humans sometimes directly come into food competition with hoolock gibbons, as some foods are consumed by both, especially fruits (Ahsan 2001).

Potential Solutions

One solution may be to combine action by the government, industry, non-government organizations, and communities in Bangladesh and northeast India to protect hoolock gibbons from enduring further forest fragmentation. Another potential solution may include offering economic incentives to landowners to contribute land to create corridors between fragmented forests and larger forests (Kakati 2006).





Content last modified: August 13, 2008

Written by Kurt Gron. Reviewed by Alan Mootnick.

Cite this page as:
Gron KJ. 2008 August 13. Primate Factsheets: Hoolock gibbon (Hoolock) Conservation . <>. Accessed 2020 February 23.