Hybridization between P. 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
As in all highly social species, communication is varied and complex. Hamadryas baboons utilize visual signals and gestures, vocalizations, and tactile communication. Visual signals include social presenting, in which a females or juveniles display their hind quarters to the male. This submissive signal differs from sexual presenting (which females do to elicit copulation) in that the hindquarters are much lower to the ground. 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. The mouth may be opened during this type of staring, although the canine teeth typically remain covered. Bobbing the head up and down is also considered a threatening behavior among hamadryas baboons. Canine teeth are displayed by a tension yawn, as another threatening gesture. This last behavior is performed only by males toward their rivals or toward predators.
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 these animals 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. All hamadryas baboons, except infants, make rhythmic grunting vocalizations when approaching another animal to signal affiliative intentions. A shrill bark is produced by all except adult males to indicate alarm, especially due to sudden disturbances.
Although chemical communication has not been reported for these animals, anubis baboon females are known to produce aliphatic acids when they are sexually receptive. These acids are thought to enhance a female’s sexual attractiveness. It is possible that similar olfactory cues may exist in P. hamadryas.
As in all primates, P. hamadryas can spend a significant amount of time engaged in social grooming. Social grooming is thought to help develop and maintain social bonds between animals. Within hamadryas baboons, most social grooming is performed by females and is directed toward the leader of the OMU. Other forms of tactile communication in this species include reassuring touches and embraces, as well as a variety of agonistic bites and slaps.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
IUCN lists P. hamadryas as lower risk/ near threatened. These primates are threatened by habitat loss, harvesting for food and for research, as well as outright persecution. CITES does not list Papio on any appendix.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Hamadryas baboons are common in irrigated agricultural areas and can be terrible crop pests. They are large animals which can be aggressive when confronted.
Negative Impacts: injures humans (bites or stings); crop pest
Hamadryas baboons are very interersting animals, and provide a great deal of entertainment to people who visit them in zoos. There are also populations of hamadryas baboons, especially on the Arabian peninsula, which attract visitors and tourists to view them. Some of these animals have been used in medical research.
Positive Impacts: research and education
Because hamadryas baboons are prey items, they form an important link in local food webs, making nutrients they obtain from plants and small animals available to larger animals. They dig for tubers, roots, rhizomes and corms, so it is likely that these animals help to aerate the soil where they forage. Also, it is likely that they play some role in dispersing seeds they eat.
Ecosystem Impact: disperses seeds; soil aeration
Papio hamadryas is omnivorous. They have been known to eat a variety of foods, including, but not limited to: fruits, tree gums, insects, eggs, acacia seeds, acacia flowers, grass seeds, grass, rhizomes, corms, roots tubers, small vertebrates. Because of the aridity of their habitat, these baboons must subsist on whatever edible items they can find.
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 hamadryas is found on the African continent in the area of the southern Red Sea, in Ethiopia, Somalia, and Eritrea. This species also occurs in the Palearctic region, in Saudi Arabia and Yemen. The latter populations often occur in close association with humans, and, although considered endemic to the region, were probably introduced there accidentally at some point during the height of the ancient Egyptian Empire.
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: palearctic (Introduced , Native ); ethiopian (Native )
Hamadryas baboons are found in subdesert, steppe, alpine grass meadows, plains, and shortgrass savannahs. Their distribution is limited by the availability of watering holes and appropriate sleeping rocks or cliffs. In parts of Ethiopia, they are found in agricultural areas and are considered crop pests.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; mountains
Other Habitat Features: suburban ; agricultural
The maximum lifespan of a captive hamadryas baboon is measured at 37.6 years. It is likely that the maximum is slightly lower in the wild
Range lifespan
Status: captivity: 37.6 (high) years.
Average lifespan
Sex: male
Status: captivity: 37.5 years.
Average lifespan
Status: captivity: 35.6 years.
Average lifespan
Status: wild: 37.0 years.
Average lifespan
Status: captivity: 28.8 years.
These monkeys are highly sexually dimorphic in size and pelage characters. Adult males weigh around 21.5 kg and females around 9.4 kg. Male pelage is basically grayish-brown in color, with the ventrum colored like the back or darker. Hairs on the cheeks are lighter, forming "whiskers" which grade into a very pronounced, bushy, silver-colored mane. The long back hairs are wavey. Females are a plain olive-brown color. The skin may be very colorful in some animals. In both males and females, the skin surrounding the ischial callosities is pink or bright red. Males have skin of a similar color on their muzzle and face, whereas females possess a muted, grayish-brown face. The tail is long, and curved, with a graceful arch at the base. The natal pelage is black, although this is lost by approximately six months of age, when it is replaced by an olive-brown coat like that of the adult female.
The head and body length has been reported as 610 to 762 mm, with the tail adding an additional 382 to 610 mm.
Range mass: 9.2 to 21.5 kg.
Range length: 610 to 762 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful; ornamentation
Average basal metabolic rate: 21.095 W.
Natural predators have been virtually eliminated from most of the range of P. hamadryas. However, it is thought that the higher levels of social organization seen in hamadryas baboons are a response to past predation. Bands undoubtedly help the baboons to defend themselves against predators, by increasing the number of adult animals to ward off attacks. Because bands and clans tend to congregate at just before reaching watering locations, a place where predators are likely to hide, such a function seems plausible. Also, troops seem to be a side effect of the desire of these animals to sleep on elevated rocks or cliffs. On explanation for this sleeping arrangement is that it inhibits access of predators to the animals. The availability of sleeping sites appears to be the principle limitation on the range of these animals.
Known Predators:
The basic social and reproductive unit in hamadryas baboons is the one male unit (OMU). Within this OMU, there is a single adult male who mates with one or more females.
Reproductive behavior in P. hamadryas is closely tied to social organization. The basic breeding unit is the OMU, in which the leader male aggressively herds females, keeping them from straggling during the foraging march, and preventing them from socializing with other males. Females typically spend most of their social time in proximity to the leader male. Most social grooming within the OMU is focused on the leader male, with females grooming him, especially his mane, face, and buttocks. The pelage characters of males can therefore be thought of as strong mate attractants, and seem to function in the maintenance of the OMU.
Because of the division into OMUs, most females have only opportunities to mate with the OMU leader. However, males may follow a number of reproductive strategies, and females may at times "sneak" copulations with males other than their unit leader.
For males without an OMU, reproductive behavior is limited, and effort seems to be expended in attempts to establish an OMU. Establishment of an OMU can occur in one of two ways. First, a subadult male may attach himself to an already established OMU as a follower. In general, a follower male remains separated from the females of the OMU, although he travels with the OMU on the daily foraging march, and sleeps near the OMU at night. There may be some potential for such follower males to mate with females, if such copulations can be conducted without detection by the leader of the OMU. Evidence for such copulations comes from the pattern of testicular development in this species, as well as a limited number of observations of such "trysts." However, the principle goal of followers seems to be to either steal females from the OMU leader, having become familiar to these females through association with the OMU, or to depose the OMU leader and commandeer his entire harem of females.
Because OMU leaders actively restrict the interactions between their females and other males, chasing, biting, or otherwise punishing females who appear to be straying, one might wonder why a female would risk incurring his wrath by engaging in copulations with other males. One might speculate that such interactions might confuse paternity if there is a turnover in leadership of the OMU, and thereby inhibit tendencies toward infanticidal behavior on the part of the new leader male.
In general, hamadryas males "respect" the social bond between other males and their female affiliates. However, rarely within a band, there is intense physical competition between males. This seems to be associated with turnover of male OMU leaders.
The second strategy utilized by males to establish a OMU is to "adopt" a juvenile or subadult female. This strategy entails much less risk to the male, because there is no overt competition for the female in question. The male will care for the little female, grooming her, carrying her if necessary, and providing what would appear to many to be parental care. When the female reaches reproductive maturity, he will breed with her. This strategy seems especially effective because females hamadryas baboons do not readily consort with single males. Once a male has established a OMU with his "adopted" female, he may become much more attractive to other females.
Females exercise some choice in their mates. Females typically disperse from their natal group between 1.5 and 3.5 years of age. About 70% of females will change affiliation to a new OMU within a period of 3 years, often choosing to join OMUs that contain other females with whom they are already familiar. Through this type of transfer, it is possible for females to maintain bonds with one another throughout their lives.
Mating System: polygynous
Hamadryas baboons breed aseasonally. Mating is based on the occurence of estrus in females, and the reproductive condition of females is generally independent of season. However, Kummer (1968) did report a peak of births in May/June and November/December.
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, alerting the male to her potentially fertile condition. During mating, there is generally a pattern of serial mounting initiated by the female, who presents her hindquarters to the male. The male mounts the female and thrusts several times. This mounting is followed by other mount/thrust episodes until the male ejaculates. Mating frequencies can be from 7 to 12.2 per hour while the female is receptive.
Gestation lasts about 172 days, after which the female gives birth to a single offspring. The neonate, weighing from 600 to 900 g, has a black coat, making it readily identifiable from older infants. Infants are completely dependent upon their mother for the first few months, until they begin to eat solid food and are able to walk on their own.
Puberty occurs between the ages of 4.8 and 6.8 years in males, and around the age of 4.3 years in females. Full size is attained in males around 10.3 years of age. Females, which are significantly smaller than males, reach adult size around 6.1 years of age.
Puberty in males is a lengthy process, and the timing of different developmental events reveals interesting details about the reproduction of these animals. Testicular development does not closely follow male growth in this species. Testes develop rapidly between the ages of 3.8 and 6 years, reaching full size prior to attainment of full adult body size. In contrast, body mass doubles between the ages of 7 and 8 years, after the testicles are fully developed. This pattern of development may indicate that subadult males, who do not possess OMUs of their own, may yet achieve some "sneak" copulations. Interestingly, the remainder of adult male secondary sexual characteristics, including the silver mane, white cheeks, and pink hindquarters, do not develop until after full adult size is reached. These characteristics are thought to function in the maintenance of the OMU, as they are very attractive to the females of the OMU and elicit large amounts of female grooming.
Females have an average interbirth interval of 24 months, although individual females have been known to have offspring as close together as 12 months. Some females have not given birth until 36 months after the birth of their previous offspring. It is likely, that as in anubis baboons, differences between females in the length of the interbirth interval are related to differences in nutritional status or social stress levels.
The average length of lactation is 239 days, but the timing of weaning may vary according to maternal condition, ecological variables, and social circumstances. Lactation can last from 6 to 15 months. The period of infant dependence is difficult to assess. Because this species is social, juveniles may continue to associate with their mothers until they disperse at or near adulthood. Also, because young females may be "kidnapped" by males wishing to establish an OMU, it is even more difficult to assess whether or not these individuals could survive without the quazi-parental care provided by the kidnapping male. In short, it would be reasonable to put the upper limit of the period of juvenile dependence at the mean interbirth interval (24 months), but to realize that this type of estimation is imprecise.
Breeding interval: Male hamadryas baboons can breed continuously, if females in their OMU are in reproductive condition. Females can produce offspring annually, but are more likely to produce an offspring every two years.annually
Breeding season: Hamadryas baboons are not seasonal breeders, and can mate throughout the year, provided females are in estrus.
Range number of offspring: 1 (low) .
Average number of offspring: 1.
Average gestation period: 172 days.
Range weaning age: 6 to 15 months.
Average time to independence: 24 months.
Average age at sexual or reproductive maturity (female): 4.3 years.
Range age at sexual or reproductive maturity (male): 4.8 to 6.8 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average birth mass: 814 g.
Average gestation period: 171 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (female)
Sex: female: 1514 days.
Most parental behavior is performed by the female. Females nurse and groom their offspring. There does not seem to be cooperative care of offspring among females, although it is not uncommon for one female in an OMU to groom the offspring of another female. 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.
Females can experience deceptive estrous cycles when a new male takes control of the OMU. This may be an adaptive parental behavior with an anti-infanticidal effect.
Males offer protection to infants by keeping control of the OMU. Males exclude other males from contact with their females and offspring, potentially inhibiting infanticide. Also, adult males maintain vigilance over the group, and are therefore likely to spot potential predators, protecting their offspring from that particular threat. Males are typically very tolerant of infants and juveniles within the OMU, and will often play with them or carry them.
The caretaking behavior of males toward to juvenile females during the formation of an OMU is quazi parental. Although from the perspective of the male this behavior is reproductive, it is parental from the perspective of the juvenile female. She obtains food, protection, warmth, and is often carried by the male, much as she would be by her own father or mother.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning
