Surili

The surilis are a group of Old World monkeys and make up the entirety of the genus Presbytis. They live in the Thai-Malay Peninsula, on Sumatra, Borneo, Java and smaller nearby islands.

Surilis are rather small, slim built primates. Their fur at the top is brown, grey, black or orange, and at the lower surface whitish or greyish, sometimes also orange, with some species having fur designs at the head or at the hips. Their German name of Mützenlanguren ("capped langurs") comes from the hair on their head, which forms a tuft. They differ from the other langurs by characteristics in the shape of their head (particularly the poorly developed or absent brow ridges, and the prominent nasal bones), in the teeth and by the size of their small thumbs. Surilis range in adult length from 40 to 60 cm (with a 50 to 85 cm long tail) and a weight of 5 to 8 kg.

Diurnal forest dwellers, they spend nearly their entire life in the trees. They live in groups of up to 21 animals (average 10 or less animals in most species) consisting of a male, several females, and their young. A few species have been observed in monogamous pairings (particularly the Mentawai langur), although this might be a reaction to the decrease of their habitat. Lone males and all-male groups have also been reported. The groups are hierarchically developed, with intergroup communication that is both vocal and postural.