It lives in tribes of up to twenty individuals and builds defensive citadels in the boughs of trees. These large, hollow nests, woven from branches and creepers and roofed with a rainproof thatch of leaves, have several entrances, usually situated where the main branches of the tree thrust through the structure. Most of the work of food gathering and building is carried out by females and young males. The adult males remain behind to defend the citadel and have developed a unique set of features to carry out their highly specialized role; horny armor over the face and chest and vicious claws on the thumb and forefinger.