L’Hoest’s monkeys live in groups consisting of a single male and 10 to 17 females and young, which form close bonds reinforced by mutual grooming. L’Hoest’s monkeys have a more terrestrial lifestyle than many other monkeys, always travelling on the ground, and, unusually for primates, running to flee from predators such as crowned hawk-eagles (2) (4), a strategy that requires great collective coordination in order to keep together as a group. To feed and to sleep, the L’Hoest’s monkeys will scale forest heights where they feed on the fruits of yellow wood, koso, parasol trees, wild custard apple, and the young leaves and shoots of various trees, shrubs and herbs. They also consume invertebrates (5), occasionally eat resins, bracken shoots, mushrooms and lichen (2), and have been seen carefully cleaning dirty dormant seeds that they have extracted from the soil (6).
When sleeping, L’Hoest’s monkeys frequent favourite tree spots, where they sleep as a group, out of reach of many predators. Newborn L’Hoest’s monkeys are brown and acquire adult colours over the first two to three months. The young are frequently observed entwining their tail with their mother’s (2).