The chacma baboon (Papio ursinus), also known as the Cape baboon, is, like all other baboons, from the Old World monkey family. It is one of the largest of all monkeys. Located primarily in southern Africa, the chacma baboon has a wide variety of social behaviours, including a dominance hierarchy, collective foraging, adoption of young by females, and friendship pairings. These behaviors form parts of a complex evolutionary ecology. In general, the species is not threatened, but human population pressure has increased contact between humans and baboons. Hunting, trapping, and accidents kill or remove many baboons from the wild, thereby reducing baboon numbers and disrupting their social structure. Taxonomy Due to hybridization between different baboon (Papio) populations across Africa, authors have occasionally grouped the entire radiation as a single species, the hamadryas baboon, Papio hamadryas. Arbitrary boundaries were then used to separate the populations into subspecies. Other authors once considered the chacma baboon a subspecies of the yellow baboon, Papio cynocephalus, although it is now recognised as a separate species, Papio ursinus. The chacma baboon has two or three subspecies, depending on which classification is followed. Grubb et al. (2003) lists two subspecies, while Groves (2005) in Mammal Species of the World listed three. This article follows Groves (2005) and describes three distinct subspecies. In the Grubb et al. (2003) paper, P. u. raucana was believed to be synonymous with P. u. ursinus. Papio ursinus ursinus Kerr, 1792 – Cape chacma (found in southern South Africa) P. ursinus griseipes Pocock, 1911 – Gray-footed chacma (found in northern South Africa to southern Zambia) P. ursinus raucana Shortridge, 1942 – Ruacana chacma (found from Namibia to southern Angola, but not accepted by all authorities as distinct. Physical description The chacma baboon is perhaps the longest species of monkey, with an adult body length of and tail length of . It is also one of the heaviest; the male weighs from with an average of . Baboons are sexually dimorphic, and females are considerably smaller than males. The adult female chacma weighs from , with an average of . Adult males can in some instances be about twice as long and three times as heavy as adult females. It is similar in size to the olive baboon, averaging slightly higher in mean body mass, and of similar weight to the more compact mandrill, the males of which weigh on average about more than