Yellow Baboon

Anubis baboons (P. anubis) are known to hybridize freely in the wild with yellow baboons, P. cynocephalus. In the Amboseli national park in Kenya, the amount of reported hybridization between these two species has increased over time. Researchers think that the increasing immigration of anubis males into yellow baboon troops is responsible for the increase noted in hybrid characters. Because the slopes of Mount Kilamanjaro are under increasing agricultural pressure, it is likely that anubis males have no alternative areas into which to emigrate.

The only differences noted in behavior of hybrid animals is that males with anubis-like features (e.g. coarser hair, longer manes, darker coloration, broader chests, and more sharply "broken" tails) tend to emigrate from their natal group as juveniles or subadults, rather than as full adults. This behavior has been seen occasionally in the anubis baboons of the Gombe preserve in Tanzania, but is not known in yellow baboons.

The hybridization between anubis and yellow baboons seems to have a long history. Interestingly, the Ibean form of yellow baboon, which has coarser hair than typical yellow baboons, a more pronounced mane, and other somewhat "anubis-like" features, is thought by some researchers to be evidence of the historical influx of anubis genes into yellow baboon populations.

As in all highly social species, communication is varied and complex. Yellow baboons utilize visual signals and gestures, vocalizations, and tactile communication.

Visual signals include social presenting, in which a female or juvenile displays its hind quarters to a male. It can also be done by a female who has approached another female with her black infant. This submissive signal differs from sexual presenting (which females do to elicit copulation), and is often accompanied by lip smacking. Staring is a threat behavior, the effect of which is enhanced by the differently colored fur in the region of the eye which is revealed when the baboon stares. Eyebrow raising reveals the lighter fur in the area of the eyelid, and is an aggressive gesture. Canine tooth display through a tension yawn is another threatening gesture. It can be directed toward a rival male, a predator, or is performed by lower-raking males toward higher-ranking males who are consorting with estrus females or who possess meat. Male baboons who are close to one another can use tooth grinding to threaten one another. Baboons retreating from high-tension situations use rapid glances to break tension. An adult male who is guarding sometimes sit with his erect penis is plain view. This penile display communicates the male’s presence to other males.

Teeth chattering and lipsmacking, although not technically vocalizations, are auditory cues of reassurance, often performed by a dominant animal when another is presenting to him.

Vocalizations made by yellow baboons include a two-phase bark, or "wahoo" call, which adult males direct toward feline predators or toward other males. It is thought to communicate the presence of the male and his arousal. Adult male yellow baboons make grunting vocalizations as a threat. Screeching is common during aggressive encounters, and can be made by any age or sex class. Subadult and adult yellow baboons produce a yakking call when retreating from a threatening animal. This call is often accompanied by a grimace of fear. A shrill bark is produced by all except adult males to indicate alarm, especially due to sudden disturbances. Rhythmic grunting may be produced by all yellow baboons except infants when they wish to signal amicable intentions to another animal. Finally, adult and subadult yellow baboons of both sexes are known to produce a dog-like bark when they become separated from the main part of the troop.

Tactile communciation is common in cercopithecines. Social grooming is used to reinforce social bonds, as well as to remove parasites and debris from the fur. Social mounting is a reassurance behavior. Anubis baboons also perform a friendly nose-to-nose greeting.

Chemical communication has not been reported for yellow baboons. However, female anubis baboons are known to produce aliphatic acids when they are sexually receptive. These acids are thought to enhance a female’s sexual attractiveness. Because there is considerable hybridization between anubis baboons and yellow baboons, and because the Ibean form of yellow baboons may have arizen originally through hybridization between typical yellow baboons and anubis baboons, it would be interesting to examine various yellow baboon populations for production of aliphatic acids.

Communication Channels: visual ; tactile ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

Papio cynocepahlus is not thought to be especially threatened at this time. However, as is true of all primates, it is listed on CITES appendix II.

CITES: appendix ii

IUCN Red List of Threatened Species: least concern

Baboons are not shy creatures, and where they come into contact with humans, they can be problematic. They are known to raid crops, and can bite humans if approached too closely.

Negative Impacts: injures humans (bites or stings); crop pest

Baboons are used heavily in biomedical and behavioral research. They are entertaining creatures enjoyed by zoo visitors and ecotourists.

Positive Impacts: ecotourism ; research and education

As predators, yellow baboons may affect the populations of prey items. As prey, they may support predator populations. Baboons may also help to disperse seeds, by passing some through their bodies undigested, or carrying fruits away from trees. They undoubtedly aid in soil aeration from digging for roots and tubers.

Ecosystem Impact: disperses seeds; soil aeration

Although generally described as frugivorous, yellow baboons are dietary generalists. they are known to eat pods, grass, sedges, seeds, fruit, roots, leaves, buds, bark, flowers, insects, and meat. They are known hunt and kill rabbits and vervet monkeys.

One feeding adaptation thought to be shared by all baboons is the ability to subsist on a relatively low quality diet. Baboons can subsist on grasses for extended periods of time. This allows them to exploit dry terrestrial habitats, like deserts, semideserts, steppes, and grasslands.

The feeding behavior of yellow baboons has been heavily studied, especially as it impacts survival of immature animals. Immatures born late in the wet season when the number of foods and food parts eaten is highest have the highest survival to four years of age. This makes sense, as there is ample food for the lactating mother. Survival of immatures is lowest for those born late in the dry season when the number of foods and food parts eaten is the lowest. Survival to two years closely parallels the feeding curves.

Animal Foods: mammals; carrion ; insects

Plant Foods: leaves; roots and tubers; seeds, grains, and nuts; fruit

Primary Diet: omnivore

Papio cynocephalus is a broadly distributed species, ranging through most of Eastern Africa south of the equatorial rain forests. These baboons occur in Botswana, Kenya, Malawi, Somalia, Tanzania, Zaire, and Zimbabwe. They are found east of the Luangwa in Zambia, in Northern Mozambique and throughout most of Tanzania.

This species is part of a complex of closely related African baboon species. We have an account of the whole genus under Papio.

Biogeographic Regions: ethiopian (Native )

Yellow baboons are found in savannah, grassland steppe, and rainforest habitats.

Habitat Regions: tropical

Terrestrial Biomes: savanna or grassland ; chaparral ; forest ; scrub forest

Other Habitat Features: agricultural

The maximum lifespan of a captive hamadryas baboon is measured at 37.5 years. A captive chacma baboon is reported to have lived 45 years in captivity. Although the lifespan of P. cynocephalus has not been reported, it is likely to be similar to these two species, although somewhat shorter than these in the wild.

Average lifespan
Status: wild: 45.0 years.

Average lifespan
Status: wild: 40.0 years.

Average lifespan
Sex: female
Status: captivity: 35.1 years.

Average lifespan
Status: captivity: 27.7 years.

These monkeys are highly sexually dimorphic. Males weigh around 23 kg and females around 12 kg. The head and body length ranges between 508 and 1,143 mm, with the tail adding an additional 456 to 711 mm to the total length. These animals have 32 teeth. The first lower premolar is modified and serves as a hone for the upper canine tooth. Males have large canine teeth, whereas the teeth of females are much smaller. There is significant geographic variation in average body size and skull size, as well as in the texture of pelage. The three forms most often described are Ibean baboons, Kinda baboons, and "typical" yellow baboons.

The orientation of the face in yellow baboons is normal, helping to distinguish them from Papio ursinus which has a downwardly flexed face. The post-orbital constriction of these animals is less pronounced than in anubis and chacma baboons. Ibean yellow baboons have large skulls. Typical yellow baboons have medium to large skulls. Kinda baboons are noted for their greatly reduced cranial size, associated smaller teeth, and weakly expressed temporal lines.

Pelage is characteristically a yellowish-brown. This overall color is produced by individual hairs which are yellow-brown for most of their length but have a black tips. In typical yellow baboons, both males and females are unmaned. However, in the Ibean form of this species, males have a weakly expressed mane. It is not at all comparable to the large mane found in Papio hamadryas, Papio anubis, and Papio papio. The head has a prominent crest on the top, produced by the longish hairs which grow upward toward the crest. This helps to distinguish this species from P. anubis which has a "flat" head. The pelage of typical and Kinda forms of this species is straight. The hair of Kinda baboons is reported to be very silky in texture. In contrast, the hairs of Ibean baboons are wavey and coarser than those of the other yellow baboons. All yellow baboons have hands and feet that are the same color as the rest of the body, and silver-colored fringes on the hands and feet.

The skin of the face and around the ischial callosities of P. cynocephalus is purplish-black in both sexes. The bare area of the rump is much smaller in this species than in P. hamadryas or P. papio.

Tail shape varies geographically. The tail of Ibean baboons resembles that of P. anubis, with the proximal portion extending straight out from the rump, and the distal 3/4 falling limp, as if the tail has been broken. Kinda baboons have a gracefully arched tail. Typical yellow baboons generally have the bent phenotype, but are variable, with some individuals showing the arched tail morphology.

In Ibean and typical yellow baboons, the natal pelage is black. This fur is replaced by the typical yellowish-brown by about 6 months of age. In sharp contrast, the natal coat of Kinda baboons is a reddish-brown color.

Yellow baboons have a somewhat "pointed" nose, and are thinner through the chest than are anubis baboons.

Average mass: males, 23 kg; females 12 kg.

Range length: head and body: 508 to 1,143 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; ornamentation

Three predator species are known for yellow baboons. The predation rate varies by population, and is estimated at between 4 and 8 percent per year. Of those who fall victim to predation, about 40% are infants, 30% are juveniles, and 13% are adult females. The remainder are adult males.

Although yellow baboons typically flee when faced with a potential predator, they have also been reported to respond aggressively to potential predators. They have been observed killing domestic dogs, mobbing smaller carnivores, such as jackals and cheetahs, and have even fought leopards and lions.

There may be a relationship between where in the troop different age or sex classes of baboons travel as it relates to risk of death from predators. However, research on this matter has been largely equivocal.

Known Predators:

• leopards (Panthera pardus)
• lions (Panthera leo)
• Cheetahs (Acinonyx jubatus)

Reproductive behavior in P. cynocephalus is closely tied to social organization. Because these animals live in multi-male, multi-female troops, there is the potential for any male to mate with any female. Males therefore compete fiercely for access to sexually receptive females. In general, a male’s ability to consort with a female and exclude other males from access to her is related to the male’s ability to compete with other males. There is therefore a correlation between male dominance rank within the troop and mating success. Larger, younger, and stronger males have a distinct advantage in this type of competition.

It should be noted that as in many other social animals, there can be other factors which affect a male’s mating success. For example, males may form alliances with other males, subverting the normal dominance hierarchy. Two males, neither of whom can dominate a third male alone, may join forces. As a coalition, these males may succeed in securing access to a sexually receptive female. Such coalitions are reciprocal, and typically occur between pairs of older males who are well acquainted with one another through mutual tenure in a troop.

Males also follow a strategy of developing "friendships" with females This enhances their opportunities to mate. In these friendships, males groom, share food, and have strong affiliative ties with particular females and their offspring. It is common for males to defend their female friends during agonistic encounters with other females, and with other males. These associations are not confined to the period during which females are sexually receptive, but span the entire gamut of the female’s reproductive life—including pregnancy, lactation, and time spent cycling. Females exhibit a preference for mating with their male friends, and therefore make consortships with their male friends more likely. In addition, because females prefer their friends as mates, they are more likely to cooperate with them in the maintenance of a consortship than they are to cooperate with other, less favored, males.

In P. cynocephalus, females mate with a variety of males during any given estrus cycle. Such multiple matings are not necessary to ensure fertilization, and may function to confuse the actual paternity of the female’s offspring. This may help to mitigate infanticidal tendencies of males.

Mating System: polygynandrous (promiscuous)

Reproduction in P. cynocephalus is related to the social structure of this species. Yellow baboons live in multi-male, multi-female troops. Mating is polygynandrous, with both males and females mating with multiple partners. Most matings occur during consortships. Consortships arise when a male, through aggression toward potential rivals, is able to maintain exclusive sexual access to a female. Females may consort with multiple males while they are sexually receptive, although they consort with only one male at a time. Because it is apparently easier for a male to maintain exclusive access to a female if the female is cooperative, there is a significant amount of female mate choice, with females preferring some partners over others.

Females characteristically have an estrous cycle of 32 days in length, however, cycle length varies between individuals and between populations. At the Tana River National Primate Reserve in Kenya, primiparous females had the longest cycles, averaging 44 days, and multiparous females had the shortest cycles, averaging 37 days. These cycles are much longer than the 32 to 34 day cycles reported in Amboseli National Park. Differences may be related to nutritional differences between populations, social differences, or they may reflect underlying genetic differences.

There is a noticeable menstrual flow for approximately three days per cycle if the female does not conceive. During the period around ovulation, the perineal skin of the female swells, alerting the males to her potentially fertile condition, and enhancing her attractiveness to them. Mating is initiated by the female, who presents her hindquarters to the male. When females are cycling, mating frequency can be from 1 to 6 times per hour. When females become pregnant, they cease to mate at all. Their pericallosal skin turns red as a result of increased blood flow to the region, alerting other members of the group to their reproductive condition.

Gestation lasts about 175 to 181 days, after which the female gives birth to a single offspring, weighing approximately 854 g. This is significantly smaller than the 1068 g neonates reported for P. anubis. The neonate has a black or reddish coat, depending upon the subspecies. This makes it easy to distinguish neonates from older infants. An infant is completely dependent upon its mother for the first few months, until it begins to eat solid food and is able to walk on its own. Age at independence is difficult to estimate, because even if the mother dies, a young baboon may continue to receive care from adult males, or other female kin. Independence is often listed as the age of weaning.

Females have an interbirth interval of approximately 21 to 27 months. This interval varies geographically, as well as according to maternal age and maternal rank. Interbirth intervals were longer at Tana River than at Amboseli, perhaps in part because the probability of infant survival to 24 months of age was greater. However, in anubis baboons, it has been shown that females who are older or have a higher rank tend to have shorter interbirth intervals, probably because these females experience enhanced nutritional status and are free from harassment by higher ranking females. The interbirth interval is also shorter if an infant dies before weaning.

Weaning occurs sometime around 1 year of age. Lactation is a huge cost for adult females, and has been shown to cause a reduction in female weight. Lower ranking and younger females probably take longer to recover adequate body weight to reproduce than do older, dominant females, explaining their longer interbirth intervals.

The onset of puberty and attainment of adult size is highly variable and is associated with nutrition levels in closely related anubis baboons. The effect of nutrition on growth is so strong that as little as 15 to 16 weeks of dietary variation in newborns can have lasting effects on overall rates of female growth, absolute adult weight, and age at menarche. This may be one reason that differences have been noted in the age of menarche in geographically separated populations.

In yellow baboons, puberty occurs between the ages of 5 and 6 years in females, and is signaled by menarche, or in some cases, first pregnancy. In males, there is greater variation in age at onset of puberty, with sexual maturation occurring between the ages of 4 and 7 years. Between 70 and 97 per cent of males emigrate from their natal troop sometime before reaching sexual maturity. Although females typically spend their entire lives in their natal troops, some transfer of females to new groups has been observed.

Breeding interval: Female yellow baboons may breed annually under some conditions, but are more likely to reproduce every other year.

Breeding season: Mating and births may occur throughout the year.

Average number of offspring: 1.

Range gestation period: 175 to 181 days.

Average weaning age: 12 months.

Range time to independence: 12 to 18 months.

Range age at sexual or reproductive maturity (female): 5 to 6 years.

Range age at sexual or reproductive maturity (male): 4 to 7 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Most parental behavior is performed by the female. Females nurse, groom, and play with their offspring. Females express different patterns of infant care, often associated with rank and age. In yellow baboons, higher-ranking females tend to be more "permissive" in their parenting than lower ranking females, who tend to be more nervous and "restrictive," preventing their offspring from moving away from them. Such differences may be related to the amount of harassment females of lower rank are likely to receive. Another difference seen in maternal behavior in this species is that older mothers are known to spend more time in contact or close to their infants and are less likely to terminate bouts of nursing than are younger females. First-time mothers are also likely to reject infants sooner than are experienced mothers. These differences may affect interbirth intervals.

Cooperative care of offspring is not present in P. cynocephalus, but it is not uncommon for females other than the mother to groom an infant, sometimes providing allomaternal care to the infant. Subadult and juvenile females who have not yet reproduced themselves are most likely to exhibit allomaternal behavior. Other factors known to affect the incidence of allomaternal behavior in most cercopithecine species include the infant’s age, and relatedness of the allomother to the mother and infant. As is the case for all baboons, infants are very attractive to other members of the social group, and are the focus of a great deal of investigation and attention, especially while they are still displaying their black natal coats. In extreme cases, females may kidnap the offspring of other females. Lower-ranking females have been reported to be subjected to this extreme form of harassment more often than have higher-ranking females. However, in an analysis of infant handling, Bentley-Condit et al. (2001) found no consistent association between mother’s rank and how often her infant was handled. Although females attempted to handle infants of females of like rank or lower more often than they attempted to handle the offspring of higher ranking females, mothers were able to successfully rebuff more than three quarters of all handling attempts.

Males have complex relationships with infants and juveniles, which in some cases may be a form of parental care. Males are known to carry, protect, share food (especially meat), groom, and play with, the offspring of their female friends. Because they are more likely to mate with their female friends than they are with other females, these infants and juveniles are more likely to be their own offspring than are other immature animals within the troop. This behavior, therefore, can be interpreted as paternal.

However, it should be noted that the relationship between adult males and these immature animals may be more complex than this. There may be some form of reciprocity involved. Adult males will often carry infants during tense interactions with other adult males. This carrying can be initiated either by the adult male or by the infant. Such contact with an infant during agonistic encounters may have the effect of inhibiting aggression by other males. The favors bestowed upon an infant used as a buffer may therefore be a form a "payback" from the adult male. However, since the tendency to use an infant as an agonistic buffer is related to familiarity with the infant and the probability of paternity, it is impossible to separate the nepotism from the reciprocity of such interactions.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning; inherits maternal/paternal territory; maternal position in the dominance hierarchy affects status of young

The yellow baboon (Papio cynocephalus) is a baboon in the family of Old World monkeys. The species epithet means "dog-head" in Greek, due to the dog-like shape of the muzzle and head. Yellow baboons have slim bodies with long arms and legs, and yellowish-brown hair. They resemble the Chacma baboon, but are somewhat smaller and with a less elongated muzzle. Their hairless faces are black, framed with white sideburns. Males can grow to about 84 cm, females to about 60 cm. They have long tails which grow to be nearly as long as their bodies. The average life span of the yellow baboon in the wild is roughly 15–20 years; some may live up to 30 years.

Yellow baboons inhabit savannas and light forests in eastern Africa, from Kenya and Tanzania to Zimbabwe and Botswana. They are diurnal, terrestrial, and live in complex, mixed-gender social groups of 8 to 200 individuals per troop. Like all other baboon species, they are omnivorous, with a preference for fruits; they also eat plants, leaves, seeds, grasses, bulbs, bark, blossoms and fungi, as well as worms, grubs, insects, spiders, scorpions, birds, rodents and small mammals. All species of baboons are highly opportunistic feeders and will eat virtually any food they can find.

Yellow baboons use at least ten different vocalizations to communicate. When traveling as a group, males will lead, females and young stay safely in the middle, and less-dominant males bring up the rear. A baboon group's hierarchy is a serious matter, and some subspecies have developed behaviors intended to avoid confrontation and retaliation. For example, males may use infants as a kind of "passport" or shield for safe approach toward another male. One male will pick up the infant and hold it up as it nears the other male. This action often calms the other male and allows the first male to approach safely.

Baboons fulfill several functions in their ecosystem, not only serving as food for larger predators, but also dispersing seeds in their waste and through their messy foraging habits. They are also efficient predators of smaller animals and their young.

Baboons have been able to fill a variety of ecological niches, including places inhospitable to other animals, such as regions taken over by human settlement. Thus, they are one of the most successful African primates and are not listed as threatened or endangered. However, the same behavioral adaptations that make them so successful also cause them to be considered pests by humans in many areas. Raids on farmers' crops and livestock and other such intrusions into human settlements have made most baboons species subject to many organized extermination projects. However, continued habitat loss forces more and more baboons to migrate toward areas of human settlement.

The two subspecies of the yellow baboon are: