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Order : PRIMATES
Family : Hylobatidae
Species : Hoolock hoolock
Head-body length : up to approx. 65 cm
Tail length : no tail
Weight : up to approx. 9 kg?
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Hoolock hoolock
(Western Hoolock Gibbon) is one of three species in the Hoolock
genus. It is listed as Endangered by IUCN (Brockelman et al, 2019).
This primate occurs in eastern Bangladesh, northeastern India (Assam) and
northwestern Myanmar (west of the Chindwin River, a tributary of the Irrawaddy
River (Ayerawady)).
To the east of the Chindwin River it is replaced by the Gaoligong Hoolock (Hoolock
tianxing) and the Eastern Hoolock (Hoolock leuconedys).
Myanmar may prove to support the most viable populations of Hoolock
hoolock, but there is little ongoing research (Brockelman et al, 2019).
Hoolock gibbons are larger than those of the widespread genus Hylobates.
Their weight is only significantly exceeded by the Siamang
(Symphalangus syndactylus).
Adult males are black with white eyebrows, and
sometimes with white on the chin. Adult females are creamy brown with darker
cheeks, and a white face ring. Infants are born all white (Francis, 2019).
As with all gibbons, this primate is strongly
arboreal, but some may briefly come to the ground to move from one group of
trees to another. Their diet comprises forest fruits, supplemented by
leaves, buds and occasional protein-rich insects (Francis, 2019).
Their calls are less complex than those of other gibbon genera, and there is
an absence of the whooping and high notes of Hylobates, for example.
Male and female calls appear to be similar; both sexes possess a laryngeal
sac (Francis, 2019).
Hoolock hoolock inhabits a range of
forest types including tropical evergreen forest, semi-evergreen forest,
tropical mixed deciduous forest and subtropical broadleaf hill forest, as
well as bamboo-dominated areas, up to elevations of 2500 metres.
Populations of this primate are threatened by the continuing loss of their
forest habitat as well as hunting for the bush meat trade. Infants are also
captured for the local pet trade.
Fig 1 : Adult female at Lawachara National Park, Bangladesh.
Photo thanks to AKM Emdadul Islam Bitu.
Fig 2 : Adult male at Hollongapar
Gibbon Sanctuary, Assam, India. Photo thanks to Miraj Hussain.
References :
Brockelman, W, Molur, S. & Geissmann, T. (2019). Hoolock hoolock.
The IUCN Red List of Threatened Species 2019: e.T39876A17968083.
Francis, C.M. 2019. A Field Guide to the Mammals of South-east Asia. Second
Edition. New Holland. 416 pp.
Acknowledgments : Audio file courtesy Yong Ding Li.
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