Geographic Distribution and Habitat
Guinea baboons are Old World monkeys that inhabit the woodlands, savannas, forests, and grasslands of the coastal West African countries of Senegal, Sierra Leone, Mauritania, Guinea-Bissau, Guinea, and Gambia. In Senegal, Guinea baboons have found a very suitable habitat in Niokolo National Park, where groups of monkeys—sometimes upwards of 500 individuals—have been found. The types of habitat in the Guinea baboons’ range varies from bush savanna to dry and gallery forests.
Size, Weight, and Lifespan
The Guinea baboon is the smallest of the baboons, weighing between 28 and 57 lb (13–26 kg). Males are slightly larger than females and can measure from 20 to 33 in (50–83 cm) in length, while females measure from 18 to 28 in (45–70 cm). These baboons can live to be up to 45 years old.
Though the Guinea baboon is the smallest baboon species, it still displays the trademark characteristics we attribute to them: their faces and rumps are hairless; their faces are black or dark purple in color, with pronounced snouts; and the females’ rumps are bright red, and swell up to attract mates. As with most baboons, their snouts are often described as “dog-like.”
Their hair is tinged with red. As a result, the Guinea baboon is sometimes referred to as the “red baboon.” The individual hairs that make up the coat are wavy, and look almost as if they were crimped. Males have manes of long hair about their shoulders and heads—a common trait among various types of baboons—and both males and females have lighter hair around the rims of their faces of a more golden hue.
Within their habitat, there are a variety of foods available to Guinea baboons. They forage for seeds, shoots, roots, fruit, and fungi. They also eat local crops, like rice, yams, or groundnuts. On occasion they eat eggs, invertebrates, and small vertebrates. In addition, Guinea baboons have been known to enter caves and lick the walls, presumably for the salt that is embedded there.
What Does It Mean?
All-male group (AMU):
A social group consisting exclusively of males, usually occurring in species with one-male groups or multi-level societies (i.e., social systems in which single males monopolize several females and there are extra males without females).
A thing or person of the same kind or category as another.
A forest that serves as a corridor along rivers or wetlands and projects into landscapes that are otherwise sparsely treed, such as savannas, grasslands, or deserts.
Multi-male multi-female group (MMU):
A social group consisting of multiple adult males and multiple adult females.
One-male group (OMU):
A social group consisting of one adult male and multiple adult females.
Using four limbs to move about. This word comes from the Latin meaning ‘four feet.’
Living on the ground.
Visit the Glossary for more definitions
Behavior and Lifestyle
Guinea baboons are, for the most part, terrestrial. They are quadrupedal (walk on all fours) and mainly active during the day. After their day begins, they set out to forage. Though they are mainly terrestrial, they seek refuge in palm or kapok trees at night to sleep in safety from predation.
The movements of the groups are dictated by male monkeys. While male congeners—such as the hamadryas baboons—are known to herd females as they change locations, male Guinea baboons are more laid back, dictating group movement through more passive means, like corralling them or setting the pace and allowing group members to follow.
Availability and quality of sleeping sites are critical and dictate where they travel to during the day. Because Guinea baboons are not adept climbers, they often jump into trees from cliffs or other high access points.
Where individuals situate themselves for sleep along a branch—with respect to proximity to the tree trunk—appears to have some significance within the Guinea baboon social structure. One theory is that adult males situate themselves close to the trunk so they can protect younger monkeys and females who sleep farther out on the branches. This way, predators cannot access the smaller, weaker, or more vulnerable monkeys. Another theory is that larger monkeys require the support of the sturdiest parts of the branch, which are closer to the trunk.
Guinea baboons are subject to predation from above: pairs of African crowned eagles will tag-team groups of baboons—one flies in to distract the monkeys, while the other attacks.
Daily Life and Group Dynamics
Many scientists believe that Guinea baboons live in One Male Units (OMUs), which is a similar hierarchical structure to the hamadryas baboon. These OMU groups center around one adult male, and include adult females and juveniles of both sexes. The dominant male presides over a harem of females, and the OMU serves as both a reproductive group and a social group. OMUs occasionally mix together to create larger groups. This is called a fusion-fission society. Groups convene and break apart depending on the varying circumstances they face. When Guinea baboons feel threatened or vulnerable, they join together (fusion); foraging, on the other hand, is typically done in smaller groups (fission). There are also groups of AMUs (All Male Units), which are comprised entirely of male baboons. They are bachelors without harems.
One interesting observation that sets the Guinea baboon apart from other species of baboons is that males are seemingly okay with sharing females with males from other groups. The norm for baboons is a high level of competitiveness with regard to mating. Female Guinea baboons interact with males from other groups more than they do with females from other groups. Female Guinea baboons also have been known to interact with their female relatives who have moved on to be part of other OMUs.
It is important to note that a study in southeastern Senegal, which began in 2007 and was published in 2011, found that Guinea baboon social structure gives cause to reevaluate our overall understanding of baboon social structures. Typically, baboon social structures are seen as resembling one of two species: those of the hamadryas baboon, which is structured around small one male groups (OMUs) that fuse into a larger group; or those of the savanna baboon, which is centered around multi-male multi-female units (MMUs). Much of the literature available regarding Guinea baboons makes the assertion that they fall into the former category; however, over the course of the study, researchers found that the Guinea baboon social structure is actually quite fluid. The size and gender composition of groups changed often, splitting into smaller groups (fission) and convening into larger groups (fusion), as well as forming smaller all male groups (AMUs), smaller one male groups (OMUs), and larger multi-male multi-female units (MMUs). They also noticed seasonal variance in group sizes. For example, groups were larger during the rainy season than the dry season. Since the organizers of the study found that Guinea baboons didn’t seem to follow typical group patterns, they conclude that there needs to be more variance in the way in which we think about baboon social systems.
Guinea baboons are highly communicative through a number of methods including touch, calls, and posture.
Touching is generally a display between monkeys who are strongly bonded.
Guinea baboons have different “bark calls” for different purposes. After feeding, for example, they will bark to reconvene. Adult males give their signature bark to direct their social groups. When they feel threatened, Guinea baboons will emit an alarm call.
All Guinea baboons make a “wahoo bark,” which is employed during agonistic behavior. On top of this, there are a variety of grunts. Males emit a deep grunt; females emit a loud, initial grunt followed by quieter grunts after mating.
Reproduction and Family
Though their familial structure is similar to that of the hamadryas baboon, the Guinea baboon’s courtship methods are a bit different. Within the OMUs of hamadryas baboon, the male typically engages the female in order to commence mating; however, female Guinea baboons are known to also approach males.
Females’ buttocks swell to indicate that they are ready to reproduce, and the gestation period for this species is six months. Once born, infants are nursed by their mothers for a period of six to eight months. Females give birth to one infant at a time, and do so every one-and-a-half to two years. There is no specific breeding season.
Because they dig for much of their food, Guinea baboons play a role in soil aeration throughout their habitat. Additionally, they serve as seed dispersers, mainly through their excrement.
Conservation Status and Threats
The Guinea baboon is listed as Near Threatened by the International Union for Conservation of Nature (IUCN, 2018). Although their adaptability to a wide variety of habitats has enabled them to remain locally common in the limited areas where they occur, they are threatened by habitat loss within their small range, resulting from large-scale agricultural expansion, persecution, and hunting. Because Guinea baboons raid crops, farmers often see them as detrimental and treat them like a nuisance species.
As with so many primate species, the best way to ensure longevity for the Guinea baboon is to protect its habitat. Fortunately, there are a number of conservation sites within this species’ range, and a healthy population exists in Niokolo-Koba National Park in Senegal. Furthermore, the species is categorized as Class B under the Convention on International Trade in Endangered Species (CITES) and the African Convention.
Written by James Freitas, December 2018