Hybridization between Papio hamadryas and P. anubis occurs along the Awash river valley in Ethiopia. The area of hybridization appears to be stable, without noticeable introgression of P. hamadryas phenotypes into anubis baboon populations or of P. anubis phenotypes into hamadryas baboon populations. The reasons for this stability are probably very complex. However, it is worth discussing two contributors to this stability in this forum.
In hamadryas baboons, the basic social unit, or OMU, is maintained as a cohesive entity through the activity of the adult male leader of the OMU. He herds females and juveniles, regulates their interactions, and prevents them from straying. Although anubis baboon males possess the same basic behaviors that would allow the males of this species to form one-male-units, there are significant differences in expression between the two species which make it impossible for male anubis baboons migrating into hamadryas territory to successfully maintain a harem of females.
For example, although male anubis baboons aggressively herd females and exclude rival males, they tend to do so only when the females are in estrus. This would prevent a male anubis baboon from maintaining a cohesive OMU in the hamadryas fashion. Also, although they form close social ties with females, they do not exhibit the "respect" of the relationship between other males and their females which is typical of hamadryas baboons. This may be related to differences in the kin associations of hamadryas and anubis baboons. Correlated with this, an anubis male trying to "steal" a sexually attractive female from a male hamadryas, would incur not just the wrath of that male, but likely the wrath of that male’s kin within the clan.
Hybrid males are known to show behavior intermediate between the two parental species. Anubis-like hybrids form lasting social bonds with anestrous females, and assume a consort-like status when the females are in estrus. However, they are unable to herd them efficiently because they do not express this behavior when the females are anestrous. The more hamadryas-like hybrids are capable of forming OMUS.
Interestingly, hamadryas males have been known to effectively integrate into anubis baboon troops. Although females mate with them, these males may still be at a reproductive disadvantage relative to anubis males. Because the mating system of the hamadryas baboon characteristically involves only one male, there has been little selection for sperm competition in this species. Hamadryas males have both relatively and absolutely smaller testicles than do anubis males. This likely results in lower production of sperm. Since female anubis baboons may mate with a number of males during their estrus cycle, lower sperm production by hamadryas males may lessen their chances for siring offspring. This may contribute to the stability of the hybrid zone.
Anubis baboons are also known to hybridize freely in the wild with yellow baboons,. 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. Interesting, the Ibean form of yellow baboon, which has coarser hair than the typical yellow baboon, 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. Anubis 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. Canine tooth display through a tension yawn is another threatening gesture. It 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. Adult males who are guarding mates sometimes sit with their erect penis in 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 it.
Vocalizations made by anubis 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 anubis baboons make grunting vocalizations as a threat, and are known to "roar" during fights. A grating roar, which is a deep, resonating call, is given by a dominant male after a fight, and is sometimes made by adult males when there is a night-time disturbance. Screeching is common during aggressive encounters, and can be made by any age or sex class. Subadult and adult olive 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. Finally, rhythmic grunting may be produced by all anubis baboons except infants when they wish to signal reassurance to another animal.
Juveniles and infants produce some vocalizations unique to their age class. These include clicking, which is a chirp-like noise which is analogous to yakking of adults. They also produce an ick-ooer sound which communicates a low level of distress.
Tactile communication 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 also been reported for this species. 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.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
Anubis baboons are not considered threatened or endangered. The IUCN Redlist rates them "Lower Risk, Least Concern." Like most primates, they are included in Appendix II of the CITES, so international trade in the animals or their parts requires government approval.
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
Baboons are large animals, and not particularly timid of humans. They are known to raid crops, and can attack and injure humans if provoked.
Negative Impacts: injures humans (bites or stings); crop pest
Anubis baboons are used in medical and behavioral research. They are socially active animals which provide entertainment for zoo visitors and ecotourists.
Positive Impacts: ecotourism ; research and education
Baboons likely play a role in aerating the soil through the digging of corms, roots, and tubers. They also are likely to disperse seeds of the fruits and grains that they eat. Baboons provide food for their predators, and also exert some affect on populations of small animals on which they feed.
Ecosystem Impact: disperses seeds; soil aeration
Anubis baboons are known to eat a wide variety of foods. They consume fruits, tree gums, insects, eggs, seeds, flowers, grass, rhizomes, corms, roots, tubers and small vertebrates.
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.
Animal Foods: birds; mammals; reptiles; eggs; carrion ; insects; terrestrial non-insect arthropods
Plant Foods: leaves; roots and tubers; seeds, grains, and nuts; fruit
Primary Diet: omnivore
Papio anubis is the most broadly distributed baboon species, ranging through most of central sub-Saharan Africa. Isolated populations occur within the Saharan region.
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 )
Anubis baboons are found in savannah, grassland steppe, and rainforest habitats.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; forest ; rainforest ; 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. anubis has not been reported, it is likely to be similar to these two species, although somewhat shorter than these in the wild.
Average lifespan
Sex: male
Status: captivity: 25.2 years.
These monkeys are highly sexually dimorphic in size and pelage characters. Males weigh around 25 kg and females around 14 kg, with some geographic variation in average size. The head and body of the average male measures 760 mm, with the tail adding an additional 560 mm. Females are smaller, with an average head and body measurement of 600 mm and an average tail length of 480 mm. Males have large canine teeth, whereas the teeth of the females are much smaller. Pelage is characteristically a dark, olive-gray. This overall color is produced by hairs with 1 to 2 alternating pairs of black and yellow-brown rings. Males possess a large mane, restricted to the anterior portion of the body, and grading into the shorter body hair toward the rear. Females lack a mane.
The skin of the face and around the ischial callosities is dark gray to black in both sexes. The bare area of the rump is much smaller in this species than in Papio hamadryas or Papio papio. Unlike some species of baboons, the nostrils of P. anubis point forward. The head is flat on top, helping to distinguish this species from Papio cynocephalus which has a prominent crest on the top of the head. The first quarter of the tail is carried erect, being held straight upward, with the remainder of the tail falling down limp, giving the tail a broken appearance. The natal pelage is black, but this fur is replaced by the typical olive-gray by about 6 months of age.
The skull of males has heavy ridges of bone on both sides of the nose, and a prominent rounded bar above the orbits. There is a sagittal crest and often a nuchal crest. Molars are large, and the first lower premolar has been modified into a hone for the upper canine. These primates have 32 teeth.
Range mass: 14 to 25 kg.
Range length: 480 to 760 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; ornamentation
Two predator species are known for anubis baboons. Leopards and chimpanzees have been known to kill these animals. Anubis baboons have been reported to mob leopards, often with adult males leading the attack. In the Gombe preserve in Tanzania, an estimated one percent of the population falls victim to predators annually. Of these, about 3/4 are infants, and 1/4 are juveniles.
Known Predators:
Reproductive behavior in P. anubis 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. This results in fierce competition between males 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.
However, as in many social animals, there are other factors which affect a male’s mating success. For example, males may form alliances with other males, which can subvert the normal dominance hierarchy. Two males, neither of whom can dominate a third male alone, may join forces and together, 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, which 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 tend to 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.
The prolonged period of sexual receptivity of females in this species is typical of primates living in multi-male, multi-female social groups. Females in monogamous or polygynous species are typically receptive for a very short time around ovulation. In P. anubis, females mate with a variety of males over a period of 15 to 20 days. 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.
Females exert some mate choice in this species. By making consortships easier or more difficult for males, females can exert some control over whom they mate with. Also, females can make it easier or more difficult for a given male to immigrate into the troop, influencing the pool of males from which they may choose mates.
Mating is initiated by the female, who presents her hindquarters to the male. The male mounts the female and thrusts about 6 times, then ejaculates. Matings are probably quick because of the intense intermale competition for access to sexually receptive females.
Mating System: polygynandrous (promiscuous)
Reproduction in P. anubis is related to the social structure of this species. Anubis 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 31 to 35 days in length. 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, and aliphatic acids are produced, alerting the males to her potentially fertile condition, and enhancing her attractiveness to them. Females are typically receptive for 15 to 20 days per cycle.
Gestation lasts about 180 days, after which the female gives birth to a single offspring, weighing approximately 1068 g. The neonate has a black coat, making it easy to distinguish 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. Females have an interbirth interval ranging from 12 to 34 months. This interval varies according to a number of factors. Females who are older or have a higher rank tend to have shorter interbirth intervals. Interbirth interval is also shorter if an infant dies before weaning.
Weaning typically occurs around 420 days of age. Lactation is a huge cost for adult females, and typically causes 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 populations where baboons are known to raid human crops, and to thereby secure greater access to nutrients than naturally foraging animals, puberty can occur much earlier. In such food-supplemented populations, males attain adult body weight between 7 and 8 years. Females reach full size by 6.5 years. In contrast, in naturally foraging populations, males do not reach full adult size until they are 7 to 10 years old, and females do not reach adult weight until they are 7 to 8 years old. 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.
In naturally foraging populations, 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, puberty begins around 6.6 years of age, when body size begins to increase rapidly, third molars erupt, and canine teeth fully erupt. Changes in male body size include increases in muscularity, which give these animals a broader profile. The mane of males also begins to develop, contributing to the increase in shoulder size. Correlated with these changes in body size, male anubis baboons undergo an increase in testicular volume. Like human males undergoing puberty, male anubis baboons are also reported to undergo a break in their voices around this time, eventually leading to a deeper sounding alarm-bark. Males typically emigrate from their natal troop just after these changes are completed.
Breeding interval: Female anubis baboons with ample food and health can breed annually. However the interbirth interval ranges between 12 and 34 months, because female condition and food supply vary.
Breeding season: Mating can occur throughout the year.
Average number of offspring: 1.
Average gestation period: 180 days.
Average weaning age: 420 days.
Average time to independence: 420 days.
Range age at sexual or reproductive maturity (female): 7 to 8 years.
Range age at sexual or reproductive maturity (male): 7 to 10 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 me more nervous and "restrictive," preventing their offspring from moving away from them. This difference has been reported in anubis baboons only up to the age of 8 weeks of infant life, but may be longer for some females or in some troops. 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.
There does not seem to be cooperative care of offspring among females in P. anubis, 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. 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 coat. In extreme cases, females may kidnap the offspring of other females. Lower-ranking females are more often subject to this extreme form of harassment than are higher-ranking females. Other factors known to affect the incidence of allomaternal behavior in other species include the infant’s age, and relatedness of the allomother to the mother and infant.
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: 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
Olive baboons (Papio anubis) are called so because of the greenish-grey coat that covers their bodies. Males have manes forming from the top of their heads through to their shoulders, the hair gradually shortening towards the back. Olive baboons also have dark grey to black faces, ears as well as ischial callosities (the thick piece of skin on their bums). They also have long, pointed muzzles, and appear quite dog-like, especially because of their quadrupedal posture and movement. Olives have very, very long tails, between 41 and 58 cm long!
With a length between 60 to 86 cm, and weighing between 15 to 30 kg, olive baboons are one of the larger baboon species, with males being about twice as large as females. Males also have large canine teeth.
Olive baboons have the largest range of all baboons, and are widespread throughout equatorial Africa, present in 25 countries. They are very adaptable and inhabit savannah areas, as well as large grassland plains and even evergreen tropical forests. They live in troops of generally between 20 and 50 members, but can sometimes consist of over 100 baboons, troop size usually determined by environmental conditions and food availability.
During the day they mostly spend their time on the ground, foraging for food, but at night they make their way up to mountain rocks or trees to avoid predators, which include large cats, hyenas, wild dogs, chimpanzees and crocodiles.
Olive baboons are omnivorous and find food on the ground, in trees and underground. Their diet consists out of grass, leaves, fruit, seeds, grains, tubers, invertebrates and even mammals, up to the size of small antelopes. Both males and females hunt.
In many areas, sadly, raiding of agricultural crops and feeding on garbage and human refuse are increasing as human populations are increasing. This close proximity to humans has been found to influence group behaviour, and it may even influence the social structure of these baboons.
Olive baboons have a gestation period of 180 days, after which one infant is born. Males compete regularly to copulate with females who are receptive for about one week a month.
For more interesting info on the olive baboon, please visit Dr. Shirley C. Strum’swebsite, Baboons R Us.Dr. Strum has done over 30 years of studies on these amazing primates, so she really knows about as much there is to know about them!
For more information on MammalMAP, visit the MammalMAPvirtual museumorblog.
The olive baboon (Papio anubis), also called the Anubis baboon, is a member of the family Cercopithecidae Old World monkeys. The species is the most wide-ranging of all baboons,[3] being native to 25 countries throughout Africa, extending from Mali eastward to Ethiopia[4] and Tanzania. Isolated populations are also present in some mountainous regions of the Sahara.[3] It inhabits savannahs, steppes, and forests.[3] The common name is derived from its coat colour, which is a shade of green-grey at a distance. A variety of communications, vocal and non-vocal, facilitate a complex social structure.
The olive baboon is named for its coat, which, at a distance, is a shade of green-grey.[5] At closer range, its coat is multicoloured, due to rings of yellow-brown and black on the hairs.[6] The hair on the baboon's face is coarser and ranges from dark grey to black.[5] This coloration is shared by both sexes, although males have a mane of longer hair that tapers down to ordinary length along the back.[3]
Besides the mane, the male olive baboon differs from the female in terms of weight, body and canine tooth size; males are, on average, 70 cm (28 in) tall while standing and females measure 60 cm (24 in) in height.[7] The olive baboon is one of the largest species of monkey; only the chacma baboon and the mandrill attain similar sizes.[8] The head-and-body length can range from 50 to 114 cm (20 to 45 in), with a species average of around 85 cm (33 in). At the shoulder on all fours, females average 55 cm (22 in) against males, which average 70 cm (28 in). The typical weight range for both sexes is reportedly 10–37 kg (22–82 lb), with males averaging 24 kg (53 lb) and females averaging 14.7 kg (32 lb). Some males may weigh as much as 50 kg (110 lb).[9][10]
Like other baboons, the olive baboon has an elongated, dog-like muzzle.[3] Its 38 to 58 cm (15 to 23 in) long tail and four-legged gait can make it seem canine.[11] The tail almost looks as if it is broken, as it is erect for the first quarter, after which it drops down sharply.[5] The bare patch of a baboon's rump is smaller in the olive baboon than in the Hamadryas baboon or Guinea baboon.[3] The olive baboon, like most cercopithecines, has a cheek pouch with which to store food.[12]
The species inhabits a strip of 25 equatorial African countries, very nearly ranging from the east to west coasts of the continent.[12] The exact boundaries of this strip are not clearly defined, as the species' territory overlaps with that of other baboon species.[5] In many places, this has resulted in cross-breeding between species.[5] For example, considerable hybridisation has occurred between the olive baboon and the hamadryas baboon in Ethiopia.[11] Cross-breeding with the yellow baboon and the Guinea baboon has also been observed.[5] Although this has been noted, the hybrids have not as yet been well studied.[5]
Throughout its wide range, the olive baboon can be found in a number of different habitats.[3] It is usually classified as savannah-dwelling, living in the wide plains of the grasslands.[13] The grasslands, especially those near open woodland, do make up a large part of its habitat, but the baboon also inhabits rainforests and deserts.[3] Uganda and the Democratic Republic of the Congo, for instance, both support olive baboon populations in dense tropical forests.[5]
The olive baboon lives in groups of 15 to 150, made up of a few males, many females, and their young.[14] Each baboon has a social ranking somewhere in the group, depending on its dominance.[14] Female dominance is hereditary, with daughters having nearly the same rank as their mothers,[14][15] and adult females forming the core of the social system.[15] Female relatives form their own subgroups in the troop.[14] Related females are largely friendly to each other. They tend to stay close together and groom one another, and team up in aggressive encounters within the troop.[15] Female kin form these strong bonds because they do not emigrate from their natal groups.[16]
Occasionally, groups may split up when they become so large that competition for resources is problematic, but even then, members of matrilines tend to stick together.[16] Dominant females procure more food, matings, and supporters. Among olive baboons in Tanzania, high-ranking females give birth at shorter intervals to infants with a higher survival rate, and their daughters tend to mature faster than low-ranking females.[16] These high-ranking females also appear to have a higher probability of miscarriages and some high-ranking matrilines have inexplicably low fertility.[16] One theory suggests this occurs due to stress on the high-ranking females, although this theory is controversial.[16] A recent study shows top-ranking females are at risk from male harassment. Males who have recently immigrated harass females in order to induce miscarriages in females they had not yet mated with, in order to impregnate them with an offspring that is his own faster. As females with living infants often have male allies protecting their infants, it makes more sense for a male to ignore infants and channel his aggression to the group's resident pregnant females who do not currently have infants instead.[17]
A female often forms a long-lasting social relationship with a male in her troop, known as a "friendship".[15] These nonsexual affiliative friendships benefit both the male and female.[16] Males benefit from these relationships because they are usually formed soon after he immigrates into a new group,[16] and helps the male integrate into the group more easily.[16] He could also potentially end up mating with his female friend in the future.[16] Females gain protection from threats to themselves and their infants (if they have any).[16] Males occasionally "baby-sit" for their female friends, so she can feed and forage freely without the burden of having to carry or watch the infant.[16] Sexually receptive females and newly immigrated males can form such friendships.[14] These relationships are sometimes enduring and the pair grooms and remains close to each other.[14] They also travel, forage, sleep, and raise infants together, as well as fight together against aggressive conspecifics.[15]
Females with high social ranks even forge friendships with multiple males at once. Another advantage of these friendships is it enables females to gain protection from the unwanted advances of males aiming to mate with them. A female who finds a male undesirable can simply rebuff his advances by calling on her male friends to chase him away, and can therefore enjoy exerting her reproductive skew. While infanticide is a reproductive strategy in males, it is costly for females, which would also explain why infanticide is a rare occurrence in olive baboons yet can be the principal cause of infant mortality in many other baboon subspecies: high-ranking females can simply rebuff a male threatening her infant, making infant-targeted aggression a reproductive disadvantage in olive baboons. This also explains the reason male olive baboons use infants as shields in aggressive encounters.[18]
Males establish their dominance more forcefully than females.[14] A male disperses,[16] or leaves his natal group and joins another group, after reaching sexual maturity.[14] Adult males are very competitive with each other and fight for access to females.[15] Higher dominance means better access to mating and earlier access to food, so naturally a great deal of fighting over rank occurs, with younger males constantly trying to rise in position.[14] Because females stay with their groups their entire lives, and males emigrate to others, often a new male challenges an older one for dominance.[14] Frequently, when older baboons drop in the social hierarchy, they move to another tribe.[3] The younger males who pushed them down often bully and harass them.[3] Older males tend to have more supportive and equal relationships than those of the younger males. The former may form coalitions against the latter.[19]
Despite being hierarchical, baboons appear to be "democratic" when it comes to deciding the direction of collective movement. Individuals are more likely to follow when multiple decision-makers agree on what direction to go rather than simply following dominant individuals.[20]
Females are sexually mature at seven to eight years old, and males at seven to 10 years.[3] The beginning of a female's ovulation is a signal to the males that she is ready to mate. During ovulation, the skin of the female's anogenital area swells and turns a bright red/pink.[21] The swelling makes it difficult to move and increases the female's chance of microbial or parasitic infection.[21] Females with more swollen anogenital areas reproduce while younger, produce more offspring per year, and those offspring have a better chance of surviving. These females also attract more males, and are more likely to cause aggressive fights between them.[14] Olive baboons tend to mate promiscuously.[14] A male forms a mating consortship with an estrous female, staying close to and copulating with her.[22] Males guard their partner against any other male trying to mate with her. Unless a female is in a multiday consortship, she often copulates with more than one male each day.[23] Multiple copulations are not necessary for reproduction, but may function to make the actual paternity of the female's offspring ambiguous. This lack of paternal certainty could help reduce the occurrence of infanticide.[3] Occasionally, male olive baboons monopolize a female for her entire period of probable conception.[23] The male protects his female from being mated by other males during consortship.[24]
Newborns have black natal coats and bright pink skin. Females are the primary caregivers of infants, but males also play a role.[14] In its first few days, the infant may be unable to stay attached to its mother and relies on her for physical support. Its grasp grows stronger by its first week and it is able to cling to its mother's fur by itself.[14] By two weeks, the infant begins to explore its surroundings for short periods, but stays near her. The distance the infant spends away from its mother increases the older it gets.[25] In general, higher-ranking females are usually more relaxed parents than females of lower rank, which usually keep their offspring close to them.[3] This difference lasts for approximately the first eight weeks of an infant's life.[3] Olive baboons do not seem to practise co-operative parenting, but a female may groom an infant that is not hers. Subadult and juvenile females are more likely to care for another's young, as they have not yet produced offspring of their own.[3] One theory for why immature females tend to seek out infants is that they can prepare for their future roles as mothers.[16] Infant baboons born to first-time mothers suffer higher mortality than those born to experienced mothers, which suggests that prior experience in caring for infants is important.[16] Adult males in the groups also care for the infants, as they are likely to be related to them.[26] Males groom infants, reducing the amount of parasites they may have, and calm them when they are stressed. They may also protect them from predators, such as chimpanzees. Adult males exploit infants and often use them as shields to reduce the likelihood that other males will threaten them.[26]
Olive baboons communicate with various vocalizations and facial expressions. Throughout the day, baboons of all ages emit the "basic grunt".[27] Adults give a range of calls. The "roargrunt" is made by adult males displaying to each other. The "cough-bark", and the "cough geck" are made when low-flying birds or humans they do not know are sighted. A "wa-hoo" call is made in response to predators or neighbouring groups at night and during stressful situations.[27] Other vocalizations include "broken grunting" (low-volume, quick series of grunts made during relatively calm aggressive encounters), "pant-grunts" (made when aggressive encounters escalate), "shrill barks" (loud calls given when potential threats appear suddenly), and "screams" (continuous high-pitch sounds responding to strong emotions).[27] The most common facial expression of the olive baboon is "lipsmacking", which is associated with a number of behaviours.[14] "Ear flattening", "eyes narrowed", "head shaking", "jaw-clapping", lipsmacking, and "tongue protrusion" are used when baboons are greeting each other, and are sometimes made with a "rear present".[27] "Eyebrow raising", "molar grinding", "staring", and "yawning" are used to threaten other baboons.[14] A submissive baboon responds with displays such as the "fear grin", the "rigid crouch", and "tail erect".[27]
One major reason for its widespread success is that the olive baboon is omnivorous and like other baboons, will eat practically anything.[5] As such, it is able to find nutrition in almost any environment and is able to adapt with different foraging tactics.[28] For instance, the olive baboon in grassland goes about finding food differently from one in a forest.[5] The baboon forages on all levels of an environment, above and beneath the ground and in the canopy of forests.[28] Most animals only look for food at one level; an arboreal species such as a lemur does not look for food on the ground. The olive baboon searches as wide an area as it can, and it eats virtually everything it finds.[28]
The diet typically includes a large variety of plants, and invertebrates and small mammals, as well as birds.[29] The olive baboon eats leaves, grass, roots, bark, flowers, fruit, lichens, tubers, seeds, mushrooms, corms, and rhizomes.[29] Corms and rhizomes are especially important in times of drought, because grass loses a great deal of its nutritional value.[29] In dry, arid regions, such as the northeastern deserts, small invertebrates like insects, grubs, worms, spiders, and scorpions fill out its diet.[29]
The olive baboon also actively hunts prey, such as small rodents, birds and other primates.[5] Its limit is usually small antelope, such as Thomson's gazelle, but will also kill sheep, goats, and chickens from farms, which may amount to around one third of its food from hunting.[5] Hunting is usually a group activity, with both males and females participating.[5] This systematic predation was apparently developed recently.[30] In a field study, such behaviour was observed as starting with the males of one troop and spreading through all ages and sexes.[30]
In Eritrea, the olive baboon has formed a symbiotic relationship with that country's endangered elephant population. The baboons use the water holes dug by the elephants, while the elephants use the tree-top baboons as an early warning system.[31]
The olive baboon is listed as least concern on the IUCN Red List because it is widespread with a large global population and not theatended by a range-wide population decline.[2] Competition and disease have possibly led to fewer baboons in closed forests. Like most other baboon species, it is routinely exterminated as a pest for crop raiding and small livestock predation.[32][33]
The olive baboon (Papio anubis), also called the Anubis baboon, is a member of the family Cercopithecidae Old World monkeys. The species is the most wide-ranging of all baboons, being native to 25 countries throughout Africa, extending from Mali eastward to Ethiopia and Tanzania. Isolated populations are also present in some mountainous regions of the Sahara. It inhabits savannahs, steppes, and forests. The common name is derived from its coat colour, which is a shade of green-grey at a distance. A variety of communications, vocal and non-vocal, facilitate a complex social structure.
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