Chacma baboon
The chacma baboon, 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 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. lists two subspecies, while Groves in Mammal Species of the World listed three. This article follows Groves and describes three distinct subspecies. In the Grubb et al. paper, P. u. raucana was believed to be synonymous with P. u. ursinus.- Papio ursinus ursinus Kerr, 1792 – Cape chacma
- P. ursinus griseipes Pocock, 1911 – Gray-footed chacma
- P. ursinus raucana Shortridge, 1942 – Ruacana chacma (found from Namibia to southern Angola, but not accepted by all authorities as distinct.
Physical description
The three subspecies are differentiated by size and color. The Cape chacma is a large, heavy, dark-brown, and has black feet. The gray-footed chacma is slightly smaller than the Cape chacma, lighter in color and build, and has gray feet. The Ruacana chacma generally appears to be a smaller, less darkly colored version of the Cape chacma.
Ecology
Habitat and distribution
The chacma baboon inhabits a wide array of habitats including woodland, savanna, steppes, and sub desert, from the grassy alpine slopes of the Drakensberg to the Kalahari Desert. During the night, the chacma baboon sleeps atop steep hills, high cliffs or rocks or in large trees, away from nocturnal predators. In daytime, water availability may limit its range in arid areas. It is found throughout southern Africa, ranging from South Africa north to Angola, Zambia, and Mozambique. The subspecies are divided across this range. The Cape chacma is found in southern South Africa; the gray-footed chacma, is present from northern South Africa, through the Okavango Delta in Botswana, Zimbabwe, Mozambique, to southwest Zambia; and the Ruacana chacma is found in northern Namibia and southern Angola.Diet
The chacma baboon is an omnivorous highly opportunistic feeder, and will eat practically anything; typical foods include fruits, seeds, grass, blossoms, bulbs, bark, insects, spiders, worms, grubs, rodents, birds, small antelope and fungi. Chacma baboon diet is thought to contain about 2 percent animal-sourced food, most of which consists of invertebrates; proportions vary between populations. Baboons are considered vermin by most African farmers due to their foraging and damage to cultivated crops and livestock. At the Cape of Good Hope in particular, chacma baboons are also known for taking shellfish and other small marine invertebrates. It is generally a scavenger when it comes to game meat, and rarely engages in hunting larger animals. One incident of a chacma baboon killing a human infant has been reported, but the event is so rare, the locals believed it was due to witchcraft. Normally, wild chacma baboons will flee at the approach of humans, though this is changing due to the easy availability of food and garbage from human dwellings in villages and towns near the baboons' habitat.Predation
Despite their formidable nature and large size, chacma baboons are vulnerable to a variety of predators. The main wild predator of adult chacma baboons is the leopard. In the Waterberg Biosphere, chacma baboon comprised 20.2% of leopard kills and 18.7% of the leopard's prey biomass. Although previously little documented, the African wild dog, a predator of similar or even slightly inferior size to male baboons themselves, in Mana Pools National Park took to chacma baboons as their main prey, comprising 44% of 118 kills. Less routine predation on chacma baboons has been reportedly committed by lions, spotted hyena, Nile crocodiles and Southern African rock pythons. The predators of infant and juvenile chacma baboons are probably even more diverse but poorly documented. It is documented that Verreaux's eagles and martial eagles have taken young chacma baboons and probable or possible predation has been committed by other eagles: crowned eagles and tawny eagles.When approaching potentially dangerous sites such as watering holes, more vulnerable members of the chacma baboon group may travel near the rear of the group but may conversely end up by the front of group out of fear if a predator approaches. The adult male chacma baboon has a fearsome defense and may assault their predators with their large, sharp canine teeth, which can seriously injure predators as formidable as leopards, and the adult males tend to be the least vulnerable members of the baboon troops. As in other monkeys, the larger, more formidable male baboons may successfully defend more vulnerable members of the troop via attacking predators if they come into sight.
Behaviour
Social organisation
The chacma baboon usually lives in social groups, called troops, which are composed of multiple adult males, adult females, and their offspring. Occasionally, however, very small groups form that consist of only a single adult male and several adult females.Chacma troops are characterized by a dominance hierarchy. Female ranking within the troop is inherited through the mother and remains relatively fixed, while the male ranking is often in flux, especially when the dominant male is replaced. Chacmas are unusual among baboons in that neither males nor females form strong relationships with members of the same sex. Instead, the strongest social bonds are often between unrelated adult males and females. Infanticide is much more common among Chacmas compared to most other baboon species, as newly dominant males will often kill infants or young baboons sired by the previously dominant male. Baboon troops possess a complex group behavior and communicate by means of body attitudes, facial expressions, vocalizations and touch.
Morning dispersal patterns
The chacma baboon often sleeps in large groups on high rocks, cliffs or in tall trees at night to avoid nocturnal predators. The morning dispersal from the sleeping site is synchronized, with all members leaving at the same time. In most cases, dispersal is initiated by a single individual, and the other members of the group decide whether or not to follow. At least five followers must be recruited for a successful dispersal initiation, and not all initiation attempts are successful. Surprisingly, the initiator's dominance status shows little correlation with successful initiation of departure; more-dominant individuals are no more likely to lead a successful departure than subordinate individuals. One study has shown that while the success rate of dispersal initiation attempts is relatively constant across all sexes, male are more likely to attempt initiation than females, and lactating females are less likely to attempt initiation than females without dependent offspring.A separate study has achieved slightly different results. While the dominance hierarchy does not play a significant role in initiating the morning dispersal, social affiliation does. Chacma baboons that play a more central role in the group are more likely to be followed during the morning dispersal. This study concluded that group members are more likely to follow the behavior of individuals with which they are closely affiliated.
Foraging behaviour
Dominance does play a role in group foraging decisions. A dominant individual leads the group to easily monopolised resources. The group usually follows, even though many subordinate members cannot gain access to that particular resource. As in morning dispersal, the inclination of group members to follow the leader is positively associated with social interactions with that dominant individual.Collective foraging behaviour, with many individuals taking advantage of the same resource at once, has also been observed. However, this behavior can be chiefly attributed to shared dietary needs rather than social affiliation. Pregnant females, who share similar dietary needs, are more likely to synchronise their behaviour than fertile females. Foraging synchronization decreases in areas with lower food density.