Anatomy and Physiology
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 33–85 cm (13–33 in). It also one of the heaviest; the male weighs from 21 to 45 kg (46 to 99 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). It is similar in size to the olive baboon and of similar weight to the more compact mandrill, which is usually crowned the largest of all monkeys. 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. Males can have canine teeth as long as 2 inches (longer than a lion's).
Geographic range and habitat
The Chacma baboon is found in southern Africa, ranging from South Africa north to Angola, Zambia, and Mozambique. Size and color vary within that range. The Cape Chacma (P. ursinus ursinus) from southern South Africa is a large, heavy, dark-brown subspecies with black feet. Another subspecies, the gray-footed Chacma (P. u. griseipes), is present from northern South Africa to southern Zambia. It is slightly smaller than the Cape Chacma, lighter in color and build, and has gray feet. The Ruacana Chacma (P. u. ruacana) is found in Namibia and southern Angola, and generally appears to be a smaller, less darkly colored version of the Cape Chacma.
The Chacma baboon inhabits a wide array of habitats, from the grassy alpine slopes of the Drakensberg to the Kalahari desert. It is omnivorous with a preference for fruits, while also eating insects, seeds, grass and smaller vertebrate animals. The Chacma baboon is generally a scavenger when it comes to game meat, and rarely engages in hunting large 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, Chacma baboons will flee at the approach of humans, though this is changing due to the easy availability of food near interaction with humans.
A dominant male baboon calls to his pride
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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 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 also common compared to other baboons species, as newly dominant males will often attempt to kill 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 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, while the success rate of 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 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 the group members are more likely to follow the behavior of individuals with whom they are closely affiliated.
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.
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.
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 prereproductive, 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.
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 to 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. 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.
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. 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 to protect her infants.
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.
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. Some troops have become a suburban menace, overturning trash cans and entering houses in their search for food. These troops can be aggressive and dangerous, and such negative encounters have resulted in hunting by frustrated local residents. This isolated population is thought to face extinction within 10 years.
The Chacma is considered to be potentially threatened under CITES Appendix 2, if populations are not monitored. 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 centres 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 human habitats, baboons are shot, poisoned, electrocuted, run over, and captured for the pet industry, research laboratories and muthi (medicine).
Snaring primates and other species for bushmeat has become a growing problem around poverty-stricken areas.
- Papio ursinus ursinus Kerr, 1792 – Cape Chacma (found in southern South Africa)
- P. u. griseipes Pocock, 1911 – gray-footed Chacma (found in northern South Africa to southern Zambia)
- P. u. raucana Shortridge, 1942 – Ruacana Chacma (found from Namibia to southern Angola)
In popular culture
In 2011, the British Television Channel ITV1 aired an eight-episode miniseries, hosted by popular British comedian Bill Bailey, with exclusive features from the series on itvWILD. The series followed the lives of three different family groups of Chacma baboons in South Africa. The series focuses on the baboons' abilities to adapt to human settlement and their complex social lives. It is generally structured within a narrative, with each adult baboon having a name and being treated as an 'actor' in the story. The three families of baboons have each developed their own ways of life; the 'Smitz' group spends most its time trying to rob food from tourists along a coastal highway, the 'Tokai' group has remained in a more natural forest area, and the 'Da Gama' group lives on the rooftops of an apartment complex. The program is the second attempt by Bailey to produce a semiserious nature documentary, and it has received good reviews.
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