| Citation |
Brockelman, W, Molur, S. & Geissmann, T. 2019. Hoolock hoolock . The IUCN Red List of Threatened Species 2019: e.T39876A17968083. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T39876A17968083.en. Downloaded on 05 February 2020. |
Description |
JUSTIFICATION
Hoolock hoolock remains Endangered, based upon a suspected population reduction of at least 50% over the period of three generations (2001-2015, 2016-2030 and 2031-2045), based on ongoing and significant levels of forest loss in Bangladesh, northeastern India and Myanmar, combined with ongoing and similarly significant levels of subsistence hunting and live capture for the pet trade throughout the species range.
RANGE DESCRIPTION
This species is found in eastern Bangladesh, northeastern India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura), and northwestern Myanmar (west of the Chindwin River). It might possibly occur in China (extreme southeastern Tibet). The distribution in India is restricted to points south of the Brahmaputra and east of the Dibang (Dingba Qu) Rivers (Choudhury 2001). Animals that once were common in the plains of Arunachal Pradesh (northeasternmost India) before that habitat was cultivated for agriculture and tea are not so any more (Islam and Feeroz 1992).
The boundary between the two species of Hoolock is the Chindwin River, which flows into the Ayerawady (Irrawady) River. At the headwaters in the north there is a hybrid zone or cline between the two species (since they are almost certainly not reproductively isolated). Das et al. (2006) reported the discovery of a population of Hoolock leuconedys in Arunachal Pradesh, northeast India, which has traditionally been considered to be part of the range of H. hoolock.
HABITAT AND ECOLOGY
This species is a forest-dweller that, depending on its locale, inhabits tropical evergreen rainforests, tropical evergreen and semi-evergreen forests, tropical mixed deciduous forests, and subtropical broadleaf hill forests. It has also been noted in bamboo “brakes” and hollock (Terminalia myriocarpa) and ajhar (Largerstroemia flosreginae) plantations. One gibbon pair in the Borajan Reserved Forest (north-east India) was observed to habitually descend from the trees to move over scrub and short bamboo especially while trying to reach the isolated food trees inside a village. This pair was found sleeping at heights of 0 m or less in bamboo clumps (Kakati 1997). Although gibbons may be moving through, or sleeping in, bamboo forest or plantations, they cannot survive in monocultures (W. Brockleman pers. comm.). Additionally, the species has been observed in two plains forest locations (Choudhury 1991). Its preferred habitat, however, is dense evergreen and semi-evergreen forests (Choudhury 2001). It has been recorded at altitudes of up to 2,500 m in Manipur, northeast India (Choudhury 2001).
Home ranges in most populations range from 8-63 ha (Ahsan 2001, Alfred and Sati 1990, Muzaffar et al. 2007, Feeroz and Islam 1992, Islam and Feeroz 1992; Islam and Feeroz 1992a, Kakati 2000, Mukherjee 1996, Tilson 1979), but unusually large home ranges of 200-400 ha were reported from Tripura and Arunachal Pradesh, northeast India (Mukherjee 1996). The western hoolock is a frugivorous species, with ripe fruits composing a majority of its diet (Ahsan 2001, Alfred and Sati 1990, Bin Muzaffar et al. 2007, Feeroz and Islam 1992, Islam and Feeroz 1992a Kakati 2000, Mukherjee 1996, Tilson 1979). A dominantly folivorous diet was reported during studies carried out in Assam’s Borajan Reserved Forest and in Tripura (Kakati 2000, Mukherjee 1996), and gibbons living in small forest fragments were observed to experience a period of almost total lack of fruit in their diet at the end of the dry season (Kakati 2000, Mukherjee 1996). Low fruit availability may contribute to the relatively large home range sizes of some populations. In northeast India, the hoolock gibbon is recognized as being an important disperser of undigested seeds from large and small fruit-bearing trees (Das et al. 2005).
THREATS
In Bangladesh, the main threats are the combined effects of habitat loss, fragmentation, human interference and hunting (Islam and Feeroz 1992, Molur et al. 2005). Hunting is universal all over Bangladesh as well as India, and may be in Myanmar also. In China, the Tibetan population could be under threat from hunting for food or non-targeted hunting, but this is not established.
In some Indian locales, these animals are rare due to large scale hunting for food and because some ethnic groups believe the gibbons have medicinal properties (Gupta 2005, J. Das pers. comm). On the other hand, observations from Arunachal Pradesh (P.C. Ray pers. comm.) suggest that hoolocks are not hunted for subsistence, and may even be cherished. Density of gibbons is still high around tribal villages of several ethnic groups; the same is true in northern Myanmar. Additionally, jhoom cultivation threatens the habitats of Indian populations, some of which are relatively isolated already (Choudhury 1991). Affecting all northeastern Indian primate populations are harvesting of bamboo for paper mills, oil mining and exploration, and coal mining, which deplete habitat and cause pollution and disturbance (Choudhury 1991). Habitat fragmentation and loss are major threats in India (Kakati 2000). Small and restricted groups may not be viable because of genetic and demographic instabilities and because they are more affected by hunting pressure and habitat loss. Many small forest fragments are reported to have only one or a few gibbon groups. These have limited chances of surviving more than a few generations without translocation (Campbell et al. 2015, Das et al. 2010).
In Myanmar, shifting cultivation is a major threat, and so is hunting. Although logging is restricted on the western side of the Chindwin, it is still considered a threat for this species (Geissmann et al. 2013). Political and ethnic conflicts have prevented the Myanmar government from promoting development and conservation activities effectively in areas of northwestern and central western Myanmar along the borders with India and Bangladesh. Thus, most conservation efforts have been concentrated within the range of Hoolock leuconedys.
USE AND TRADE
This species is hunted for food throughout most of its range. See the Threats section for more details.
CONSERVATION ACTIONS
This species is listed on CITES Appendix I and on schedule I of the Indian Wildlife (Protection) Act of 1972. Overall, it is found in 30 protected areas in India (Choudhury 2001) and many others throughout its range. |
