Order : PRIMATES
Family : Hylobatidae
Species : Hylobates agilis

Head-body length : up to 65 cm
Tail length : no tail
Weight : up to 7.3 kg (male), 6.8 kg (female)

Hylobates agilis (Agile Gibbon, Black-handed Gibbon) inhabits tall dipterocarp forest in most of Sumatra, northern Peninsular Malaysia (north of the Perak and Kelantan rivers) and extreme southern Thailand. On the Malay Peninsula its range is bounded on the north and south by the White-handed Gibbon Hylobates lars. Altitude range is from swampy lowlands to montane (up to 1400 metres in Sumatra) (Geissmann et al, 2020).

This exclusively arboreal ape moves through the canopy by the typical brachiation used by other gibbons. Their diet comprises ripe fruits, figs, flowers, leaves and insects; the latter provide a source of protein.

Two colour phases of this species occur; a dark phase, which predominates on the Malay Peninsula, and a blonde phase which is common in Sumatra. Dark forms also have dark feet and hands, in contrast to the White-handed Gibbon. The hands of pale forms have similar, or slightly darker, fur as the rest of the body. (Francis, 2019)

Males and females both have a pale band across the brow. Males also have pale cheeks and sometimes a pale beard; females typically lack these features. (Francis, 2019)

The louder calls of this species, which can be heard from a great distance, sound similar to those of the White-handed Gibbon. Other, quieter calls may differ however. (Francis, 2019)

IUCN (Geissmann et al, 2020) categorise this primate as Endangered due to continued loss of forest habitat and poaching; these threats are particularly concerning in Sumatra.

Figs 1 and 2 :  A dark-phase Agile Gibbon seen at a fruiting tree shortly after noon, near the base of Maxwell Hill (Bukit Larut), Perak, Peninsular Malaysia.  This individual is tentatively identified as a sub-adult male, based on the slightly paler fur on the front of the cheeks and beneath the chin. Photos thanks to Grace Pang.

Fig 3 : Tall, primary, lowland dipterocarp forest on the steep, western slope of Maxwell Hill (Bukit Larut).


References :

Francis, C.M., 2019. Field Guide to the Mammals of South-east Asia. Second Edition. Bloomsbury Publishing. 416 pp.

Geissmann, T., Nijman, V., Boonratana, R., Brockelman, W, Roos, C. & Nowak, M.G. 2020. Hylobates agilis. The IUCN Red List of Threatened Species 2020: e.T10543A17967655.