In the pale headed saki the head and body length are 12 to 28 inches and the tail length is 10.2 to 21.8 inches. The weight is 2.4 to 5.75 pounds. The male is uniformly black with a white crown, face and throat. The female is predominately blackish or brownish. Sakis are essentially diurnal and arboreal, descending only occasionally to lower branches or shrubs in their search for food. They seldom descend to the ground or climb to the treetops because their major predators (small cats, large snakes and avian raptors) inhabit these niches. While usually moving on all fours, they are capable of making long leaps through trees, and have been observed running in an erect posture along horizontal branches. Pale-headed sakis sleep curled on a branch like a cat, and sometimes hang by their hind feet when feeding. Sakis are monogamous.