Hamadryas baboon

Lore & Background

The hamadryas baboon exhibits strong sexual dimorphism: males develop a silver-white mane around age ten and are nearly twice as large as females, which are brown all over with reddish to dark brown faces. Infants are very dark brown or black and lighten after about one year. The species lives in arid areas, savannas, and rocky regions, requiring cliffs for sleeping and water sources. Its diet is omnivorous, varying with the wet and dry seasons, and includes blossoms, fruits, seeds, grasses, roots, tree gums, leaves, eggs, insects, spiders, worms, scorpions, reptiles, birds, and small mammals.

Reader's Guide

The hamadryas baboon is notable for its unusual four-level social system, called a multilevel society, which is strictly patriarchal. Most social interaction occurs within one-male units (harems) led by a male who guards up to ten females. Two or more harems form clans of related males with an age-based hierarchy; two to four clans form bands of up to 400 individuals; several bands may gather into a troop at sleeping cliffs. Males limit female movements through herding and threats, and fights over females are common. Unlike most other baboon species, male hamadryas baboons remain in their natal clans or bands. Females do not display dominance hierarchies within harems, as the harem male suppresses aggression. The species was sacred to the ancient Egyptians, particularly associated with Thoth, and appears in art as a recorder of the Weighing of the Heart and as one of four baboons guarding the lake of fire in Duat.

Did You Know?

• The hamadryas baboon is the northernmost of all baboon species.
• Males develop a silver-white mane at around ten years of age.
• The species has a four-level social system: harems, clans, bands, and troops.
• In ancient Egyptian religion, the hamadryas baboon was sacred to Thoth and served as a recorder of the Weighing of the Heart.

Physical Form & Sexual Dimorphism

The hamadryas baboon presents one of the most striking visual contrasts between the sexes found in the primate world. Adult males, once they reach roughly ten years of age, grow a dramatic silver-white mane and mantle that sets them apart from every other member of the group. Their bodies can stretch to about eighty centimetres in length and their mass ranges from twenty to thirty kilograms, making them nearly double the size of their female counterparts. Females, by contrast, remain uniformly brown with reddish to dark brown faces and carry no cape at all, weighing only ten to fifteen kilograms with a body length of forty to forty-five centimetres. Both sexes share a tail that adds another forty to sixty centimetres and terminates in a small tuft. Newborns arrive in a very dark brown or near-black coat that gradually lightens over the first year of life. Sexual maturity arrives at different paces: females are ready by around four years, while males do not reach that stage until somewhere between five and seven years old.

The Four-Tier Social Architecture

What distinguishes the hamadryas baboon from nearly every other primate is its four-level social architecture, a structure researchers call a multilevel society. At the base sits the one-male unit, or harem, which pairs a single dominant male with as many as ten females and sometimes a younger follower male who may be kin to the leader. Two or more harems that repeatedly reunite form a clan, within which the males are close relatives bound by an age-based dominance ranking. Clans then cluster into bands of two to four groups, collectively numbering up to four hundred individuals that travel and sleep together. Males almost never leave their natal band, while females may be transferred or traded between bands by the males who control them. Bands occasionally clash over food or territory, with the adult harem leaders serving as the primary combatants. Solitary males who hold no harem roam freely within the band. At the highest level, several bands may converge to form a temporary troop, typically at a sleeping cliff.

Patriarchal Control & Male Competition

Among baboons and macaques, the hamadryas stands out for its strictly patriarchal social order. Males actively restrict female movement, herding them with visual displays and resorting to grabbing or biting any female who strays too far. Competition between males takes the form of harem raids, where a challenger attempts a takeover of a female from a rival. These confrontations are accompanied by a rapid eyelid flash and a yawn baring the teeth, and infants are sometimes seized as hostages during the scuffle. Yet males within the same clan, being close relatives, tend to honour kinship bonds. Females are not passive in this system: they express clear preferences for particular males, and rival males generally respect those preferences. A female who shows little favour toward her harem male becomes a far easier target for a rival. Young males, often the follower males, can found their own harems by coaxing immature females into following them or by force, then mating with the female once she matures. Aging males who lose their females to younger rivals often shed weight and their coat shifts to a brown hue resembling that of a female.

Life in the Arid Margins

As the northernmost of all baboon species, the hamadryas occupies a range stretching from the Red Sea coast of Eritrea through Ethiopia, Djibouti, and Somalia, as well as the Sarawat Mountains of Yemen and Saudi Arabia. It is locally extinct in Egypt. Its world is one of arid plains, savannas, and rocky terrain, and it depends on cliffs both for sleeping and for locating water. As an omnivore adapted to dry conditions, its diet shifts with the seasons. In the wet months it feeds on blossoms, fruits, seeds, grasses, rhizomes, corms, wild roots, tubers, bark, tree gums, and acacia leaves. When the dry season arrives, it falls back on Dobera glabra foliage and sisal leaves. It also takes eggs, insects, spiders, worms, scorpions, reptiles, birds, and small mammals including antelope. Water access is equally seasonal: in the wet period pools are close at hand, but in the dry months the baboons concentrate around up to three permanent waterholes, resting there in the midafternoon and digging small drinking holes just a short distance from the natural sources. The region's relative scarcity of natural predators, compared with central or southern Africa, offers the species a notable survival advantage.