A striking island monkey that looks as if it’s been outlined in ink and then dipped in sunset colours. Adults have mostly black fur, but their face is framed by a neat white “halo” of hair and a pale band across the back of the neck, while the chest, belly and inner limbs glow reddish-brown to orange. Their long tail, often as long as the rest of the body put together, acts like a balancing pole when they move through the trees. Newborns look completely different: they’re almost pure white at first, with pale skin, and only gradually darken over their first few months until they match the adults.

This langur lives only on Siberut Island, part of the Mentawai Islands off the west coast of Sumatra in Indonesia. It’s a true island specialist, found nowhere else in the world. Its home is the lowland rainforest and swampy forest that still cover parts of the island, where the air is hot and humid and the canopy is thick with vines and epiphytes.

Siberut langurs are diurnal and arboreal: they are active during the day and spend almost all their time in the trees, rarely descending to the ground. They move through the mid and upper canopy in small, quiet groups, often just a handful to perhaps a dozen animals, and will sit for long periods resting or grooming between feeding bouts. Like many leaf monkeys, they have a big, round belly not because they are fat but because their stomach is enlarged and chambered, full of microbes that help them digest tough plant material.

But for a “leaf monkey,” the Siberut langur has a surprisingly sweet tooth. Its diet is unusually rich in fruit compared with many of its close relatives. Groups spend a lot of time visiting fruiting trees and feeding on soft pulp and seeds, topping this up with young leaves and the occasional flower or shoot.

Distribution

Country

Population est.

Status

Year

Comments

Indonesia

46,000-47,000

Official estimate

EN

2015

Sumatera