Sarawak Langur

Also known as the Bornean banded langur, this is the most taxonomically tangled of Borneo's leaf monkeys: two colour forms are described, a black morph (jet-black body with a pale chin, wrists and tail underside) and an eastern 'tricolour' form (red-orange head, shoulders, sides, thighs and calves with white cheeks and underside, and black arms, hands, feet and dorsal stripe). Both have bald, grey-skinned, gaunt-looking faces. Mixed troops containing both colour forms have been reported, and researchers genuinely disagree about whether these are true subspecies or simply colour morphs of one variable population — present that as an open question, not a settled fact.

One of the rarest primates on Earth: a 2015 survey found it at only five confirmed sites in Sarawak (Samunsam Wildlife Sanctuary, Tanjung Datu, Gunung Pueh, Similajau and Maludam National Parks), with a combined population estimated at just 200–500 individuals across roughly 5% of its historic range. Critically Endangered (IUCN, assessed 2020), driven by oil-palm conversion.