Chacma baboon

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 behaviors, 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.

Chacma baboon[1]
Male in Kruger National Park, South Africa

Least Concern  (IUCN 3.1)[2]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Genus: Papio
Species:
P. ursinus
Binomial name
Papio ursinus
(Kerr, 1792)
Subspecies

3 ssp., see text

Geographic range

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.[3] 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,[4] while Groves (2005) in Mammal Species of the World listed three.[1] 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.[4]

  • 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
Chacma baboon skeleton

The chacma baboon is perhaps the longest species of monkey, with a male body length of 50–115 cm (20–45 in) and tail length of 45–84 cm (18–33 in).[5][6] It also one of the heaviest; the male weighs from 21 to 45 kg (46 to 99 lb) with an average of 31.8 kg (70 lb). Baboons are sexually dimorphic, and females are considerably smaller than males. The female chacma weighs from 12 to 25 kg (26 to 55 lb), with an average of 15.4 kg (34 lb).[7][8][9][10] 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 1 kg (2.2 lb) more than a chacma baboon, the females weigh 3 kg (6.6 lb) less than the female chacma. While the mandrill is usually crowned the largest of all modern monkeys, going on total length and average (but not maximum) body weight between the sexes, the chacma baboon appears to be the largest extant monkey.[9][11] The chacma baboon is generally dark brown to gray in color, with a patch of rough hair on the nape of its neck. Unlike the males of northern baboon species (the Guinea, hamadryas, and olive baboons), chacma males do not have a mane. Perhaps the most distinctive feature of this baboon is its long, downward-sloping face.[12][13] The canine teeth of male chacma baboons have a mean length of 3.86 ± 0.30 cm (1.52 ± 0.12 in) at the time they emigrate from their natal troop. This is the time of greatest tooth length as the teeth tend to wear or be broken thereafter.[14]

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
Trapped up tree by Kalahari lions
Tswalu Kalahari Reserve, South Africa

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.[2] During the night, the chacma baboon sleeps atop steep hills, high cliffs or rocks or in large trees, away from predators. In daytime, water availability may limit its range in arid areas.[2] 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 (south of the Zambezi), to southwest Zambia; and the Ruacana chacma is found in northern Namibia and southern Angola.[2]

Diet

The chacma baboon is an omnivorous opportunistic feeder, and will eat practically anything; typical foods include fruits, seeds, grass, blossoms, bulbs, bark, insects, worms, rodents, birds, small antelope and fungi (the desert truffle Kalaharituber pfeilii). They are fond of various crops and will also kill and eat sheep, goats and poultry. They are considered vermin by most African farmers.[15] At the Cape of Good Hope in particular, chacma baboons are also known for taking shellfish and other small marine invertebrates.[16] 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.[17] 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.[18]

Behavior

Social organization

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.[19] 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.[20] 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 trees at night to avoid 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.[21] 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 (as measured by grooming behavior and time spent with other members) 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.[22]

Foraging behavior
Chacma baboons have been observed to adopt orphaned young

Dominance does play a role in group foraging decisions. A dominant individual (usually the alpha male) leads the group to easily monopolized 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.[23]

Collective foraging behavior, 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 synchronize their behavior than fertile females. Foraging synchronization decreases in areas with lower food density.[24]

Adoption

Adoption behavior has been observed in chacma baboons. Orphaned baboons whose mothers have disappeared or died are often too small to care for themselves. In one study of nine natural orphans and three introduced orphans, all but one orphan were adopted by another member of the group. The individual that was not adopted was 16 months old, four months older than the next oldest orphan, and was old enough to survive on its own. Adoption behavior includes sleeping close to the orphaned infant, grooming and carrying the orphan, and protecting it from harassment by other members of the troop. Both males and females care for infants, and care does not depend on the infant's sex. Additionally, all caregivers are pre-reproductive, only four or five years of age. The two major theories explaining this behavior are kin selection, in which caregivers take care of potentially related orphans, and parental practice, in which young caregivers increase their own fitness by using an orphan to practice their own parental skills.[25]

Friendship
Chacma baboons mating at Cape Point in South Africa

Males and female chacma baboons often form relationships referred to as "friendships". These cooperative relationships generally occur between lactating females and adult males. The females are believed to seek out male friendships to gain protection from infanticide. In many baboon species, immigrant alpha males often practice infanticide upon arrival in a new troop. By killing unrelated infants, the new male shortens the time until he can mate with the females of the troop. A female with dependent offspring generally does not become sexually receptive until she weans her offspring at around 12 months of age. However, a mother usually becomes sexually receptive shortly after the death of her offspring.[26]

Grooming strengthens bonds between individuals in groups

This protection hypothesis is supported by studies of stress hormones in female baboons during changes in the male hierarchy. When an immigrant male ascends to the top of the male dominance hierarchy, stress hormones in lactating and pregnant females increases, while stress hormones in females not at risk of infanticide stay the same. Additionally, females in friendships with males exhibit a smaller rise in stress hormones than do females without male friends.[27]

The benefits of friendship to males are less clear. A male is more likely to enter into friendships with females with which he has mated, which indicates males might enter into friendships to protect their own offspring and not just to protect that female's future reproductive success.[28] These friendships may play a role in the mating system of chacma baboons. A female will often mate with several males, which increases the number of potential fathers for her offspring and increases the chances she will be able to find at least one friend willing to protect her infants and assist in caring for them.[29]

Female chacma baboons have been observed to compete with each other for male friends. This may be the result of one male having a high probability of paternity with multiple females. These competitions are heavily influenced by the female dominance hierarchy, with dominant females displacing subordinate females in friendships with males. Generally, when a more-dominant female attempts to make friends with an individual which is already the friend of a subordinate female, the subordinate female reduces grooming and spatial proximity to that male, potentially leaving her offspring at higher risk of infanticide.[30]

Relationship with humans

Conservation

The chacma baboon is widespread and does not rank among threatened animal species. However, in some confined locations, such as South Africa's Southern Cape Peninsula, local populations are dwindling due to habitat loss and predation from other protected species, such as leopards and lions.[31] Many troops have become a suburban menace in their search for food, overturning garbage cans, and literally breaking into cars and houses where they cause much damage. These troops can be dangerous and aggressive, and they will even steal food directly from people. These negative encounters have resulted in the baboons being hunted and poisoned by frustrated local residents. This isolated population is thought to face extinction within 10 years.[18]

Chacma baboons live in proximity to humans and are frequently killed as vermin

The chacma is listed under Appendix II of CITES as it occurs in many protected areas across its range.[2] The only area in South Africa where they are monitored is in the Cape Peninsula, where they are protected.

Observations by those working hands-on in South Africa's rehabilitation centers have found this species is damaged by human intervention; troop structures are influenced, and over the years a significant loss in numbers has occurred. Because they live near and invade human habitats, baboons are regularly shot, poisoned, electrocuted, beaten, run over, and captured for the pet industry, research laboratories and muthi (medicine).[32] Despite this, assessors working for the IUCN believe there are no major threats that could result in a range-wide decline of the species.[2]

gollark: 1³/3 isn't 1.
gollark: * + c
gollark: The integral of x² is x³/3, yes.
gollark: The curve is x², so that's what you integrate.
gollark: My calculator says it is → it must be.

See also

References
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  2. Hoffmann, M. & Hilton-Taylor, C. (2008). "Papio ursinus". IUCN Red List of Threatened Species. 2008: e.T16022A99710253. doi:10.2305/IUCN.UK.2008.RLTS.T16022A5356469.en.{{cite iucn}}: error: |doi= / |page= mismatch (help)
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