Geographic Distribution and Habitat
Chacma baboons are found throughout southern Africa. They are found in Angola, Botswana, Mozambique, Namibia, South Africa, and Zambia. These baboons live in woodlands, savannas, steppes, sub deserts, and montane regions. In the Western Cape region of southern African chacmas are often referred to as the cape baboon or even the savanna baboon.
Water availability limits their overall range, since they depend largely on water sources. Predation risk also influences their habitat choice. Chacma baboons will often retreat to large trees, hills, and cliffs during the night.
Size, Weight, and Lifespan
Chacma baboons are one of the largest baboon species. They are sexually dimorphic in size, meaning there are pronounced size differences between sexes. Males weigh around 57-68 lb (26-31 kg), while females weigh about 31 lb (15 kg). Males are about 59 in (150 cm) long from head to tail. Females tend to be a tad more slender, measuring 43 in (110 cm) long from head to tail.
Chacma baboons live up to 30 years in the wild.
Chacma baboons are large primates with dog-like snouts and large prominent canines (females tend to have smaller canines). They have large skulls and a narrow upper face. They also have long limbs and a relatively short tail.
These cape baboons have short and coarse hair. Unlike their brothers (such as hamadryas, anubis, and guinea baboons), they do not have manes, but have only small clumps or tufts of hair around their faces. The males tend to have these tufts of hair growing close together around their necks. The pelage (or hair) of chacma baboons can vary from light gray to a dark olive-brown color. Their limbs, hands, feet, and back are usually covered in darker hair, such as black or dark brown. Their underparts and snout are light tan and brown. In addition, chacmas have a dark purplish black face. Overall, their hair color is very distinct. Each individual hair is black with a single yellow-brown band. Light hairs usually have a black tip.
Infant chacma baboons are typically covered in a black coat, which is replaced with adult fur by the age of 6 months.
It is important to note that there is geographic variation in pelage coloration of chacma baboons. A subspecies of these baboons, called gray-footed baboons, are found in the northeastern region of the chacma range. Gray-footed baboons differ in color from cape baboons and are smaller in size. They have gray fur and grayish arms, hands, and feet. Their hairs have a different banding pattern than cape baboons, which have black tips and black rings. In gray-footed baboons, the narrowing of the skull behind the eye sockets or the post orbital constriction, is much more reduced than in cape baboons.
Chacma baboons are omnivorous, feeding on many plant and animal species. They consume grass, flowers, leaves, seeds, roots, tree gum, and tubers. Their diet also includes fruits (especially figs and pinnata), eggs, insects, and small vertebrates.
The baboons are often regarded as pests in the Cape region. Usually they will flee when humans approach; however, with a copious amount of food around, this is changing. Baboons that live near human settlements raid food from homes, lodges, or picnic areas in national parks. Sometimes humans directly feed them, reinforcing their behavior and further attracting them to human-populated areas.
Behavior and Lifestyle
Chacma baboons are quadrupedal and terrestrial primates. When they run, their style is similar to a horse’s gallop. They spend most of their day on the ground foraging for food, but they often spend their nights high up in trees or on rock formations to sleep and to possibly escape nearby predators like leopards, lions, and the African rock python.
Grooming is an important social activity that strengthens relationships among a troop. Male to female grooming is used during courtships and nursing. Females partner with certain males for protection, especially for their infants. Often times, females seek protection if a male recently immigrated into the group and has attained alpha status. Aggressive alpha males will resort to infanticide—killing baboon babies that are still dependent on their mother for milk. Thus, females make friendships with males to reduce this risk.
Female to female grooming may take place when a subordinate female wants to gain acceptance from a higher ranking female. In addition, reciprocal grooming builds strong relationships among related or non-related females typically of the same rank or age.
Chacma baboons have a habit of turning over stones in search of food. So it is pretty easy to spot where a troop of chacmas were once foraging.
Chacma baboons have cheek pouches the size of their stomachs to store food.
In water-scarce areas, such as Namibia, chacmas can survive up to 20 days without water by eating foods with high water content.
Members of a troop sleep together, forage together, and travel together. Their troops consist of 20 to 80 individuals. Chacma baboons have the largest home ranges and daily ranges of savanna baboon species. Home ranges have been reported to be between 3.5 and 13 miles (5.6-20.9 km). Daily ranges have been reported to be between 1 and 9 miles (1.6-14.5 km). Their daily travels can be limited by availability of watering sites and sleeping locations. Sleeping sites located high on rocks and cliffs must be reached by nightfall to avoid predators. Therefore, chacma baboons have very complex group systems in order to coordinate and communicate to find sleeping locations, as well as other valuable resources.
Cape chacma baboon populations have a very complex multi-male, multi-female social structure. Occasionally one-male units (OMUs) form within the multi-male, multi-female society, resulting in aggressive behavior between males. Typically, one male will interact with a group of females and their immature offspring. Once the male offspring are mature, they emigrate out of their natal group and set out for a new troop. Once they find a new troop, they establish dominance of that troop. This involves aggressive behavior between males. The “winner” of the encounter establishes dominance over the “loser.”
Mountain populations of chacmas in east South Africa form OMUs more often than other savanna baboon species. OMUs form due to random changes in demography or the environment. Random changes often consist of an increase or decrease in troop size depending on how many births or deaths there are in the troop. Environmental factors also impact OMUs, such as changes in climate, which cause a reduction or increase in resources. Another factor may be simply a temporary separation of one male with a group of females that happened to get split up from a larger troop while foraging.
There are a wide range of behavioral differences in different types of groups, including foraging patterns, sexual behaviors, intragroup relations, and intergroup relations. Baboons in OMUs tend to feed on small fruit patches. Everyone in the group is able to feed and will feed until all the fruit is gone. In multi-male troops, many baboons do not get a chance to feed, simply due to exclusion, and they often leave fruit patches while there is still plenty of fruit left. Multi-male groups tend to forage more for grass, tubers, and plants such as Egyptian lotus (Nymphaea caerulea). OMUs avoid these foods and forage more for fruit trees like figs and seeds.
Males do not maintain lifelong ties with their kin. Female kinship forms the stability of chacma baboons society. Since females do not emigrate from their natal groups, female kin maintain lifelong associations. Within a group of chacma baboons, there is a dominance hierarchy of matrilines (a line of descent from a female), which means that a certain individual female is of high rank in the society. An individual female occupies a place in the dominance hierarchy under her mother and younger sisters. These dominance relationships develop from infancy. Interestingly within the matriline, the dominance relationships of sisters are inverse of birth order: the younger sisters are higher ranked than the older sister. These relationships sometimes cause differential treatment of offspring as well as others in the troop. The benefits of having this type of dominance society is that high ranked females have access to the best mates, have better access to food, receive more grooming, and get harassed less.
Female kin relationships can last multiple generations. They act differently toward one another than unrelated females. They help one another during disputes. Female baboons help not only their offspring, but aunts, nieces, grandmothers, and granddaughters. Thus, a very tight bond is formed, which is nearly unbreakable. However, they rarely fuss over an arrival of a new female into the troop. This can explain why female kinship has such stability.
Chacma baboons engage in a variety of visual, vocal, and tactile communication. They use facial expressions and body postures to communicate levels of excitement, arousal, or anger. Friendly and non-threatening behavior consists of soft grunts, avoiding eye contact, and retracting lips to display their clenched teeth. Presentation of the rump is used as an invitation by sexually receptive females, but it can be used as a signal by both sexes.
Aggressive expressions are associated with staring fixed at an individual, displaying canines, grinding teeth, and thrusting body postures that may include shaking of trees or grass.
Chacma baboons exhibit many vocal signals, which can be combined with visual signals. They use a well known double bark called “bokkum” as an alarm or aggressive signal; it’s given by only high-ranking males when there is aggression either between troops or within their troop. It is also used for a predator signal or for when a male communicates his presence or arousal. Lower-ranking males use a shrill single bark. This is expressed when there is a sudden disturbance or when one part of the troop rejoins another. Grunts are used for contentment, desire, or mild aggression. For example, females in estrus use a muffled growl or grunt during copulation. Chacma baboons also exhibit a range of clicking, yakking, screeching, and grunting sounds.
They also use deceitful signals. Infants can scream in alarm to get their mothers’ attention to attack another female who has food that the infant wants. Subordinates often use false alarms and false reactions to distract attacking dominant baboons.
Juvenile and infant chacma baboons sometimes produce unique vocalizations. They produce a nasal “chattering” call during play. When in distress, juveniles produce an “ick-ooer” sound to signal that something is wrong.
Some of their tactile communication consists of touching noses, which is a friendly greeting signal. Chacma baboons also partake in social grooming, which reinforces social bonds.
The reproductive behavior in chacma baboons is closely tied to social organization. In multi-male, multi-female troops, it is likely that any male can mate with any female. Thus, males compete for mates. There is also a link between a male’s rank within the troop and mating success. Most of the time, males with a higher rank have a better ability to compete for mates. Larger, stronger, and sometimes even younger males have the best success.
Females exhibit a preference for mating with their male friends, since they prefer their friends as mates. When a female is ready to mate, she presents her rump to those males. Sometimes females develop an alliance with new males that immigrate into the troop to help their chances of success. There is a significant amount of female mate choice in chacma baboons.
After 175-180 days, females give birth to a single offspring. The infant has a black coat, making it distinguishable from older offspring. For the first few months, the infant is completely dependent on his or her mother, usually until he or she can eat solid food and is able to walk on his or her own. Females have an interbirth interval ranging from 18-24 months. An interbirth interval is the time between the birth of one offspring to the birth of the next offspring; this ultimately shapes the families structure. Chacmas, therefore, give birth to a new offspring between 18-24 months after they had their last infant. Older females and females who have a higher rank tend to have shorter periods between births. Females who have an infant that dies before weaning also have shorter period between births.
Nursing the young is very important in primate species. Chacma baboons tend to wean their offspring around 420 days of age. Like most adult females, lactation is a huge cost for chacma mothers. Some females lose a significant amount of their body weight. Lower-ranking females and younger females may take more time to recover from reduction in body weight to reproduce than older dominant females. This is because dominant females have better access to resources and feeding sites than do lower ranking females. This would also explain longer interbirth intervals in younger and lower-ranking females.
Most of the parental care is done by the females. They nurse, groom, and play with their offspring. Cooperative care of offspring by other females has not been found in chacma baboons. However, it is common in other baboon species for females other than the mother to groom and play with or watch over an infant. Males, on the other hand, have complex relationships with offspring. Sometimes they offer care, such as in savanna baboon species; they will groom, feed, and protect their young. Other times adult males will carry their young while having agonistic encounters with other males, hinting that the infant may be used as a buffer or as “payback” from the other male.
The onset of puberty depends on nutrition levels. The impact of nutrient levels on growth can take as little as 15-16 weeks to have lasting effects on overall rates of growth, weight, and age at menarche (the first occurrence of menstruation) in females.
It takes up to 3 years of age for female chacmas to fully mature. Male maturity takes up to 5 years of age. Within about a year, individuals reach their adult size.
Chacma baboons dig for tubers and roots, which aerates the soil while they forage for food. This plays a large role in making nutrients they obtain from small plants and animals available to larger animals. They also play a role in dispersing the seeds they eat.
The chacma baboon is listed as Least Concern on the International Union for Conservation of Nature Red List of Endangered Species since the species is widespread and abundant (IUCN, 2018).
Their current population is stable and many live in protected areas. Currently, there are no major threats to chacma baboons, but occasionally they will be shot as pests. Baboons may be frequently poisoned by humans, especially for being pests or raiding their crops. Baboons are also hunted locally, and in South Africa dead baboons are sold in markets for traditional medicine use. This is not considered a major threat to this species.
Other baboon species may experience habitat loss due to overgrazing, agricultural expansion, irrigation, and the growth of human settlement. These issues pose a threat, but chacma baboons may be less affected by these challenges.
Chacma baboons live in numerous protected areas across their range. The African Wildlife Foundation (AWF) works with communities to help protect these species and to help find solutions so humans and monkeys can reside in the same areas. They use technology, such as Geographic Information System (GIS) to identify near threats. This allows for more efficient conservation plans. AWF also provides training on how to be more sustainable and more productive with agriculture activities. The AWF works with rural communities that live close to wildlife. They will help build schools in exchange for practicing conservation. By working with these communities they are able to provide solutions and educate future generations into practicing conservation for the species and wildlife around them.
In South Africa, the Cape Peninsula Baboon Research Unit and a Baboon Management Team (BMT) also work to lessen conflict between humans and baboons, which helps contribute to sucessful management of baboons in the region.
Written by Tara Covert, July 2018