The hamadryas baboon is a species of baboon from the Old World monkey family. It is the northernmost of all
the baboons, being native to the Horn of Africa and the southwestern tip of the Arabian Peninsula. These
regions provide habitats with the advantage for this species of fewer natural predators than central or
southern Africa where other baboons reside. The hamadryas baboon was a sacred animal to the ancient
Egyptians and appears in various roles in ancient Egyptian religion, hence its alternative name of
Apart from the striking size difference between the sexes (males are often twice as large as females), which
is common to all baboons, this species also shows sexual dimorphism in coloration. The fur of males is
silver-white in color and they have a pronounced cape (mane and mantle) which they develop around the age of
ten, while the females are capeless and brown. Their faces range in color from red to tan to a dark brown.
Males may have a body measurement of up to 80 cm (31 in) and weigh 20-30 kg (44-66 lb); females weigh 10-15
kg (22-33 lb) and have a body length of 40-45 cm (16-18 in). The tail adds a further 40-60 cm (16-24 in)
to the length, and ends in a small tuft. Infants are dark in coloration and lighten after about one year.
Hamadryas baboons reach sexual maturity at about 51 mo for females and between 57 and 81 mo for males.
The baboon has an unusual four-level social system called a multilevel society. Most social interaction
occurs within small groups called one-male units or harems containing one male and up to ten females which
the males lead and guard. A harem will typically include a younger "follower" male who may be related to the
leader. Two or more harems unite repeatedly to form clans. Within clans, the dominant males of the units are
probably close relatives of one another and have an age-related dominance hierarchy. Bands are the next
level. Two to four clans form bands of up to 200 individuals which usually travel and sleep as a group.
Both males and females rarely leave their bands. The dominant males will prevent infants and juveniles from
interacting with infants and juveniles from other bands. Bands may fight with one another over food, etc.,
and the adult male leaders of the units are usually the combatants. Bands also contain solitary males that
are not harem leaders or followers and move freely within the band. Several bands may come together to form
a troop. Several bands in a troop also often share a cliff-face where they sleep.
The hamadryas baboon is unusual among baboon and macaque species in that its society is strictly patriarchal.
The males limit the movements of the females, herding them with visual threats and grabbing or biting any
that wander too far away. Males will sometimes raid harems for females, resulting in aggressive fights. Many
males succeed in taking a female from another's harem, called a "takeover". Visual threats are usually
accompanied by these aggressive fights. This would include a quick flashing of the eyelids accompanied by a
yawn to show off the teeth. As in many species, infant baboons are taken by the males as hostages during
fights. However, males within the same clan tend to be related and respect the social bonds of their kin.
In addition, females demonstrate definite preferences for certain males, and rival males heed these
preferences. The less a female favors her harem males, the more likely she will be successfully taken by a
rival. Young males, often "follower" males, may start their own harems by maneuvering immature females into
following them. The male may also abduct a young female by force. Either way, the male will mate with the
female when she matures. Aging males often lose their females to followers and soon lose weight and their
hair color changes to brown like a female. While males in most other baboon species are transferred away
from their male relatives and into different troops, male hamadryas baboons remain in their natal clans or
bands and have associations with their male kin.
Hamadryas baboons have traditionally been thought of having a female transfer society with females being
moved away from their relatives of the same sex. However, later studies show female baboons retain close
associations with their female kin throughout their lives. Females can spend about as much time with other
females as they do with the harem males, and some females will even interact with each other outside of their
harems. In addition, it is not uncommon for females of the same natal group to end up in the same harem.
Females can still associate and help their extended families despite their interactions being controlled by
the harem males.
Females within a harem do not display any dominance relationships as seen in many other baboon and macaque
species. The harem males suppress aggression between the females and prevent any dominance hierarchies from
arising. Despite this, some social differences between the females occur. Some females are more socially
active and have a stronger social bond with the harem male. These females, known as the "central females",
stay in closer proximity to the harem male then the other females. Females that spend most of their time
farther from the harem male are called "peripheral females".
Reproduction and parenting
Like other baboons, the hamadryas baboon breeds aseasonally. The dominant male of a one-male unit does most
of the mating, though other males may occasionally sneak in copulations, as well. Females do most of the
parenting. They nurse and groom the infant and one female in a unit may groom an infant that is not hers.
Like all baboons, hamadryas baboons are intrigued by their infants and give much attention to them. Dominant
male baboons prevent other males from coming into close contact with their infants. They also protect the
young from predators. The dominant male tolerates the young and will carry and play with them. When a new
male takes over a female, she develops sexual swellings which may be an adaptation that functions to prevent
the new male from killing the offspring of the previous male. When males reach puberty, they show interest in
mothering young infants. They will kidnap the infants by luring them away from their harems and inviting them
to ride on their backs. This is more often done by "follower" males. This kidnapping can lead to dehydration
or starvation for the infant. The harem leader would retrieve the infants from their kidnappers, which
is mostly an act to protect their offspring.
Zoológico de Vallarta A. C.
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