Both males and females of Aotus trivirgatus are similar in size with a body length of 24 to 47 cm. Tail length ranges from 22 to 42 cm. Coats range from grizzled brown, gray or reddish backs and off white to orange undersides. Coat color changes from one geographical location to another and for this reason, among others, A. trivirgatus is often separated into many different species or sub-species by different researchers. Aotus trivirgatus is the only nocturnal primate of the neotropics [See comments below]. They have the largest olfactory bulbs and accessory olfactory bulbs of all the New World monkeys presumably due to their reliance on smell during nocturnal activity. They also have large brown/orange eyes. The distinctive markings of the face include a triangular black patch between the eyes and black stripes on the sides, framing their otherwise white face.
(Macdonald 1997, Hershkovitz 1983, Wright 1994)
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Average mass: 800 g.
Average basal metabolic rate: 2.499 W.