Northern White-cheeked Crested Gibbon

The northern white-cheeked gibbon is a species of gibbon native to Southeast Asia, closely related to the southern white-cheeked gibbon, with which it was previously considered conspecific. Males are black all over except for distinct white cheek patches, a prominent tuft on the crown and a gular sac; females are reddish-tan, lack the tuft and have a crest of black or dark brown fur from the crown to the nape. Both sexes have unusually long arms, 1.2 to 1.4 times as long as the legs (Wikipedia, general species account).

Today it is found only in northern Vietnam and northern Laos; it was formerly known from Yunnan in southern China and was confirmed extinct there in 2013. In Vietnam at least 22 groups were confirmed in Pu Mat National Park, and a monitoring programme in Xuan Lien Nature Reserve found 64 groups and 182 individuals in 2020, up from 41 groups and 127 individuals in 2011. It is arboreal, diurnal and sociable, living in groups of up to six, believed to be territorial, and sleeping in high branches, often embracing one another. Its calls are among the most complex of any gibbon.