Primate Diversity: Hamadryas Baboons

Hamadryas one-male unit

Hamadryas baboons (Papio hamadryas hamadryas) are “desert baboons” and range within the Horn of Africa (Ethiopia, Eritrea, Sudan, Somalia, and Djibouti) and the southwestern Arabian peninsula (South Arabia and Yemen). The baboons (genus Papioare commonly divide into five general categories. The others are  olive/anubis baboon, yellow baboons, Chacma baboons, and guinea baboons (geladas are within a separate genus, Theropithecus). The five types were originally considered separate species. However, due to the hybridization with anubis baboons, and genetic evidence, they are now typically classified into subspecies of Papio, although there still is ongoing taxonomic debates (Swedell, 2006).

Because Hamadryas baboons played an important role in Egyptian mythology, they are sometimes referred to as the ‘sacred’ baboons (Kummer, 1995). Although they were not native to Egypt, they were brought into Egypt and often kept as pets. They were considered to be an incarnation of Thoth, the god of Wisdom, and given sacred status. As a result, hamadryas baboons were often depicted in artwork.

Statue of Thoth as a baboon (circa 1400 BC) in the British Museum

Statue of Thoth as a baboon (circa 1400 BC) in the British Museum

One of the most striking features of hamadryas is marked sexual dimorphism in size and pelage. Males weigh 40-50 lbs, and have sharp canines with a CP3 complex. Like other baboons, their extended prognathism is due to their long, large canine roots. In addition males have long lion-like manes around their heads and upper bodies. Females, however are around half the size as males (20-25 lbs), and lack the fluffy manes of the males.

The other striking feature about hamadryas is their social organization, which differs from the other baboons. They live in a hierarchical, fission-fusion society. Unlike the flexible subgrouping of chimpanzees and spider monkeys, these societies have ordered grouping patterns that center around small groups. These groups are one-male units (OMU; also referred to as harems or families) that include one dominant breeding male (“leaders”),  one to five females, offspring, and sometimes subordinate “follower” males. Along with older male juveniles and solitary males, these OMUs join other units to form a stable band. Bands are groups of that travel cohesively throughout the day. At night, they join other bands to congregate at sleeping cliffs to form a troop. Another grouping level, called clans, were identified as subgroups of multiple OMUs within the band; however, this grouping is not recognizable at all study sites (Swedell, 2006).

Hamadryas female grooming juvenile

Dominant leader males aggressively herd females to stay close to their unit by biting their necks. Females copulate almost exclusively with the dominant males. Other leaders of OMU generally “respect” other leader males’ claim to their females. Males usually stay within their bands, but leave their natal OMU as juveniles. The male juveniles, along with solitary males, travel along with the OMU but predominantly socialize with the other juvenile and solitary males. Juvenile females are herded by established males into an existing OMU, or by solitary males into a new OMU. Takeover of the females from an OMU can occur through aggression, but dominate males may also allow “follower” males to take over their OMU. Although previous research indicated that the main social bonds within OMU were between females and the dominant males, Swedell (2006) found that in group containing multiple females, particularly larger groups, females form strong bonds as well.

Hamadryas and anubis baboons live alongside each other in a hybrid zone in Ethiopia (Kummer, 1995). While they do interbreed and produce fertile offspring in these zones, species-typical behaviors are often a stumbling block. Hamaydryas males actively herd, and the females in turn follow the males. However, anubis baboons have multi-male, multi-female societies in which females can mate with multiple males. When hamadryas males try to herd anubis females, presumably to establish their own OMU, female anubis do not follow them unless they are in estrus. Similarly, anubis females in hamadryas bands respond to male herding attempts by fleeing, rather, than following. Nonetheless, some immigrants are able to fit in well enough to reproduce.

Anubis baboons grooming

References

Kummer H. 1995. In Quest of the Sacred Baboon: A Scientist’s Journey. Princeton: Princeton University Press.

Swedell, L. 2006. Strategies of Sex and Survival in Hamadryas Baboons: Through a Female Lens. Upper Saddle River, NJ: Pearson Pearson Prentice Hall.

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About Dr. Michelle A. Rodrigues

I am a primatologist/biological anthropologist who studies comparative social behavior and endocrinology. My dissertation research focused on stress and friendship in female spider monkeys. Most of my graduate research was conducted at El Zota Biological Field Station, with a little help from the spider monkeys at Brookfield Zoo, IL. I have also studied howler monkeys, rhesus monkeys, bonobos, and chimpanzees, as well as participated in studies on gorillas, pachyderms, and big cats. Currently, I am a postdoctoral research associate at the University of Illinois, where I am examining how female friendship and social support mediate stressors experienced by teenager girls and female scientists. I've taught courses in introductory biological anthropology, world prehistory, and co-instructed a field course in primate behavior and conservation at El Zota. I love teaching about primates and evolution!
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2 Responses to Primate Diversity: Hamadryas Baboons

  1. pounmp13 says:

    Neck biting is an interesting, but not surprising, way that baboons shows dominance. As the neck is an extremely vulnerable spot, allowing a male to bite you there shows the females submission. I was surprised by the sacred baboon as I always associated the cat with the sacred animal of Egypt.

  2. Pingback: Week 4: Primate Hybridization | shawmk11

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