Yellow Baboon, Papio cynocephalus
YELLOW BABOON
Papio cynocephalus
Geographic Distribution and Habitat
The yellow baboon (Papio cynocephalus) occurs in several countries across the African continent, including Ethiopia, Kenya, Malawi, Mozambique, Somalia, Tanzania, and Zambia. The most prominent geographical borders of this territory include Mount Kenya and the Tanya River in Kenya, and the Luangwa River and Zambezi Valley in Zambia. Throughout their range, these monkeys live amongst open woodlands, savanna, dry bushlands, steppes, gallery forests, and mangroves.
One of the most dangerous habitats for these animals is the “fire-climax Miombo woodland”, a unique African ecosystem where the dominating plant species have adapted to survive frequent fires. Although frequent fires help maintain the ecological integrity of the woodland, they still pose a safety risk to many other species. Luckily, yellow baboons are highly adaptable and can adjust their lifestyles according to any environment.
Temperatures may range anywhere between 48 and 90 degrees Fahrenheit (8.89 and 32.2 degrees Celsius).
In 1766, Carl Linnaeus, a Swedish biologist and physician, discovered the yellow baboon on a trip to the African continent. Upon discovery, Linnaeus scientifically named them “Papio cynocephalus”. The origin of their name comes from the Greek words “kynos” and “kephalikos”, meaning “dog” and “head”. Aptly named, the translations refer to the quadrupedal stance and elongated muzzles portrayed by both baboons and canines.
In 2001, Colin Grooves, formally known as an important professor of biological anthropology at the Australian National University, recognized P. cynocephalus as a separate species from other baboons. Interestingly, further taxonomic research has proven that there are two yellow baboon subspecies: the traditional yellow baboon (Papio cynocephalus cynocephalus), and the northern yellow baboon (Papio cynocephalus ibeanus).
Size, Weight, and Lifespan
Yellow baboons are sexually dimorphic, meaning that they have physical differences based on their gender in addition to those that define their sex. The average yellow baboon male weighs 57 pounds (25.8 kilograms) and has a body length of 4 feet (120 centimeters). The average female yellow baboon weighs 24.25 pounds (11.0 kilograms) and has a body length of 3.2 feet (97.6 centimeters).
In the wild, the average lifespan of the yellow baboon is 27 years.
Appearance
As their name implies, yellow baboons are named for the yellow-brown fur that covers nearly their entire body, including their inner limbs, cheeks, and some parts of their muzzle. Males, which appear slightly different from females, have longer fur at the nape of their necks. For both males and females, the majority of the face is colored black and coated with light, fine fur. The brow ridge is covered in yellow-gray fur.
The brow ridge, also called the supraorbital ridge, acts as facial support for a baboon’s strong facial bones, which comes in handy when they bite down on hard food items with strong force. The ridge helps distribute the stress of powerful bites across the skull, preventing damage to the facial bones. In social hierarchies, pronounced brow ridges also serve as a visual sign of dominance and aggression.
Yellow baboons walk quadrupedally and have non-prehensile tails. Although the tail cannot be used for grasping, it provides them with balance and stability while traveling, running, and climbing.
Diet
When it comes to their diet, yellow baboons are extremely selective, opportunistic eaters. Known as “eclectic omnivores”, they can consume all edible parts of a tree, including leaves, gums, inner pith, seeds, seed pods, and rotten wood. The two most important tree species to a yellow baboon are the fever tree (Acacia xanthophloea) and the umbrella tree (Acacia tortilis), also known as “tortilis trees”. Not only are these trees considerable food sources for yellow baboons, but they also provide shelter and help regulate their ecosystem’s water levels. Due to their preference for swampy habitats, they also contribute to the area’s biodiversity.
Considering weather patterns, on average, most areas in which yellow baboons live receive about 13.4 inches (0.34 meters) of rainfall, per year. Rain falls during two distinct periods, November to December and March through May. Since water is a relatively unreliable resource in south-central Africa, to meet their daily intake requirements, yellow baboons must live within close proximity to standing water sources, such as a lake or stream. Their most notable water sources are the Luangwa River, and the swamps and groundwater forests created by the underground drainage of Tanzania’s Mount Kilimanjaro.
Other common foods for these animals include grass, fruits, flowers, termites, beetles, ants, reptiles, birds, eggs, small vertebrate prey, and other primates, such as grivet monkeys (Chlorocebus aethiops) or lesser bush babies (Galago senegalensis). Additionally, yellow baboons have been seen living close to humans, seizing the opportunity to regularly forage for food at garbage sites.
Similar to dogs, yellow baboons have a protruding muzzle and sharp canine teeth. Although both males and females have sharp canines, there is some variation in length and sharpness between the sexes. Compared to females, males have longer, sharper upper canine teeth that are about 2 inches (5.08 centimeters) in length. These are especially beneficial during aggressive interactions with other males, and when feeding on large prey. To help with resource storage, yellow baboons also have cheek pouches. Cheek pouches are specialized pockets on the inside of their cheeks that can be used to store food for later consumption. This is especially useful when traveling for long periods of time.
Behavior and Lifestyle
Beginning at around 7:00 in the morning, for up to 10 hours, the average yellow baboon may spend 70 to 75% of its daily life foraging. When foraging, resource availability plays an important role in determining how far a troop travels. Considering this, it is unsurprising that a yellow baboon’s home range may vary seasonally. Specifically considering fruit and plant availability, more time is spent foraging at the end of the rainy season, compared to an African dry season. For example, if plants are prevalent during the rainy season, a baboon may travel only 2.11 miles (3.4 kilometers), rather than 4.47 miles (7.2 kilometers) during a dry season, simply due to accessibility and convenience.
After returning to their sleeping site in the evening, yellow baboons retreat to the trees for rest, in addition to safety. At night, it is very important for them to protect themselves from all potential predators which include: lions (Panthera leo), cheetahs (Acinonyx jubatus), leopards (Panthera pardus), spotted hyenas (Crocuta crocuta), jackals (Lupulella mesomelas), pythons (Python sebae), servals (Leptailurus serval), caracals (Caracal caracal), and genets (Genetta genetta).
Within yellow baboon troops, hierarchy is very important. According to recent research, some male subspecies have adopted unique behavioral strategies to maintain social order and avoid confrontation. For example, males have been identified using infants as a ticket to approach other males. In these situations, one male will pick up the infant and hold it up as it greets the other male. Although the action may be confusing for the infant, this behavior can be beneficial because it allows individuals to stay calm in an otherwise potentially heated exchange.
The average yellow baboon troop contains anywhere between 30 to 80 individuals and typically has 7 to 8 males, and twice as many females. When traveling as a large group, members often follow a specific hierarchical order. In this order, the troop’s most dominant males lead in the front, followed by females and their offspring, while lesser males bring up the rear. According to various research studies, females and juveniles form the troop’s familial core. The home range for any single troop is usually around 5,930 acres (2,400 ha), and the daily range of a troop is 3.6 miles (6 cm) on average.
Within the species, adult males compete very fiercely for mates, especially against other males. Not only will males aggressively defend females from other troop members to gain their interest, but males are known to form “friendships” with females to enhance their mating opportunities. Dominant males are known to guard their reproductive partners from others, permitting the female to feel safe and stay close to the male. This behavior is known as mate guarding.
Both males and females form a linear dominance hierarchy, in which the highest-ranking members have access to a larger amount of the troop’s valuable resources, such as food and mating opportunities.
There is a correlation between male dominance rank within the troop and mating success—larger, younger, and stronger males have a distinct advantage. Of course, there can be exceptions to this rule. Males can form reciprocal alliances with other males to subvert the normal dominance hierarchy. Essentially, two weaker—and usually older—males can join forces to out-compete one stronger male.
There are also “friendships” between male and female yellow baboons that often enhance a male yellow baboon’s chances to mate. The friendship also provides opportunities to share food, groom, and affiliate with particular females and their offspring. It is not uncommon for males to defend their female friends and their offspring during hostile encounters.
However, males do not maintain life-long social ties with their kin, so it is female kinship that forms the core and stability of yellow baboon society. Female baboons do not emigrate from their natal groups like males do, so they are able to form life-long associations. Within a troop, there is a dominance hierarchy of matrilines (a line of descent traced from a female ancestor to a descendant) that is very stable over time because it is not continually challenged by the arrival of new females in the troop like males.
In general, yellow baboons communicate by producing various vocalizations and by using their bodies to create visual displays.
Considering vocalizations, yellow baboons produce sounds such as barking, grunting, and screeching. They may also chatter their teeth to show aggression or smack their lips to show reassurance to other troop members.
Visual cues such as staring, eyebrow-raising, and teeth displaying, are also effective forms of communication, especially for males when they try to portray dominance over other males.
Yellow baboons are extremely sociable nonhuman primates and as such, they have developed complex forms of communication that range from threatening to friendly gestures. For example, if antagonized, a male might choose to shake some branches and yawn to display his sharp canine teeth to communicate visually, before resorting to physical fighting. If a situation does escalate into a physical dispute, friendly signals like lip-smacking and grooming can be used as reconciliation. Yellow baboons also utilize vocalizations and tactile communication.
Visual signals include, “social presenting” in which a female or juvenile displays her hindquarters to a male for mating purposes, “staring,” which is an aggressive gesture, “eyebrow-raising”—an aggressive gesture that reveals the lighter fur in the area of the eyelid, “canine tooth display,” another aggressive gesture usually directed toward other males or a predator, “tension yawning” to display canines (see above), and “tooth grinding,” an aggressive gesture to threaten another male.
Auditory cues include “teeth chattering or grinding,” an action that can be heard when two males are threatening each other, and “lip-smacking,” which is a reassuring display as the lips are protruded and smacked together.
Vocalizations include “two-phase bark,” a wahoo call that adult males direct toward feline predators or other males, “grunting” emitted by adult males as a threat, “screeching,” commonly emitted during aggressive encounters during any age or from either sex, “yakking,” a call emitted when retreating from a threatening animal, “shrill barking,” which is produced by all except adult males to indicate alarm, especially due to sudden disturbances, “rhythmic grunting,” which may be produced by all yellow baboons, except infants, when they wish to signal amicable intentions to another animal, and “dog-like barking,” produced when they become separated from the main part of the troop.
Tactile communication includes social grooming which reinforces social bonds and removes parasites and debris from the fur.
Yellow baboons live in multi-male, multi-female troops and have a polygynous mating system where males mate with multiple females. They have multiple partners throughout their reproductive lives. In general, both males and females reach sexual maturity between the ages of four and six.
Before mating, female baboons present swollen genitalia during their estrous period, the period when a female mammal is sexually receptive and ready to conceive. As an evolutionary advantage, having swollen genitalia helps the females attract mating partners, evidently increasing their reproductive fitness. Reproductive fitness refers to an organism’s ability to successfully pass on its genes to the next generation of offspring. Once pregnant, the female will birth her offspring after 180 days, or six months. This is her gestation length.
Although twins are possible, baboon mothers usually birth one offspring at a time. Birthing usually occurs at night, when troops are most protected in their homes, and the mother presents labor signs for one to two hours. After giving birth to her infant, the mother becomes the primary caregiver and takes on nursing, grooming, and playing responsibilities. Depending on her age and rank, she may seek help from other females, in which case she will share some of her parental responsibilities. The sharing of parental responsibilities is also known as alloparenting.
After one year, the infant should be completely weaned from its mother.
When it comes to food, yellow baboons are opportunistic eaters. Not only does their foraging style help with seed dispersal, but because they are good diggers, they also help aerate soil by digging.
Seed dispersal is the process by which animals unintentionally transport seeds to new locations after dropping, spitting, or excreting them. Environments benefit from seed dispersal because the technique helps plant species avoid competition with others, therefore increasing the chances of successful germination and population growth throughout a wider area. This phenomenon can be very important for habitat regeneration and increased biodiversity.
Soil aeration is the process of creating openings in soil to allow air, water, and nutrients to reach plant roots more easily, helping them respire and release energy. Soil aeration is critical for an ecosystem because, without proper aeration, roots become deprived of oxygen, leading to a weakened body, and potential death. In the event that the plant dies, eventually, every species that relied on that particular plant as a food source would be affected in some way. On a large scale, the more plants that are derived from oxygen, the weaker the ecosystem.
In addition to plant species, yellow baboons can also have a positive ecological impact on non-plant species. Because they are efficient predators, hunting practices may keep certain species in check, preventing them from becoming too dominant within an ecosystem. If a species becomes too dominant, it can significantly disrupt the balance of that ecosystem by out-competing other species for resources, leading to declines in biodiversity, food chain disruptions, and potential extinction for some species.
The International Union for Conservation of Nature lists the yellow baboon as Least Concern (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.
According to the IUCN Red List of Threatened Species, there are no major threats to this species across its range, although some populations are under pressure from agriculture and development projects. As other wildlife species decline and human populations increase, there is also a potential for hunting practices to increase. Although the hunting of yellow baboons is not widespread, some cases have been reported through the species’ geographical range.
Yellow baboons are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Yellow baboons are present in many protected areas across their geographical range. For example, these animals are protected in Amboseli National Park and Tsavo East National Park in Kenya; Ruaha National Park, Mikumi National Park, Udzungwa National Park, Mkomazi National Park, and Selous Game Reserve in Tanzania; and Liwonde National Park in Malawi.
Unfortunately, this species is susceptible to the spread of Treponema pallidum, the causative agent of syphilis. Syphilis is a bacterial sexually transmitted infection that can cause mild to serious health issues. In baboons, the transmission of syphilis from an infected individual, through sexual contact, can cause genital ulcers and severe distortions of the genitalia, in addition to enlarged lymph nodes. In the wild, it is unclear whether or not baboons serve as a reservoir for human infection, although humans serve as a reservoir for baboon infection. In order to make these distinctions, research and ongoing monitoring for hunting pressure and disease transmission is recommended to assess the species’ future, long-term.
As always, the effects of global climate change should be monitored to provide species protection for these animals.
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Written by Brooklynne Mitchell-Arno, November 2024