They are active during the day and are stay mostly in the trees, going to the ground only at natural mineral sources. They are threatened by habitat destruction, and hunting for their meat. They live in small groups of 6-8 with 1 male and 2 or more females. The Mentawai leaf monkey, however, is monogamous and lives in mated pairs. The thumb is particularly short.
Females form the stable core and have a clear stable hierarchy.
Males without females live alone or in small bachelor groups. Harems of 1 male with 4-6 females and their young. Males keep a look out for predators, keeps the group together and patrols the territory. In good weather, they sleep outside, but during cold winters, they shelter in caves. Other species are in serious danger in some parts of their distribution due to habitat destruction and hunting.