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Hamadryas baboons sitting together on a tree trunk in the outdoor enclosure at the DPZ Anton Säckl

Hamadryas baboons

Distribution

Hamadryas baboons (Papio hamadryas) are native to Northeast Africa and the southwestern Arabian Peninsula, surrounding the southern Red Sea. How they originally migrated from Africa to the Arabian Peninsula remains unclear. It is believed that Hamadryas baboons may have crossed the Red Sea during the Late Pleistocene, between 130,000 and 12,000 years ago, possibly using a land bridge near the Bab-el-Mandeb Strait, which connected the Red Sea to the Gulf of Aden due to lowered sea levels during the ice age. Hamadryas baboons are the northernmost baboon species and the only one found outside Africa.

Physical Characteristics

Hamadryas baboons display distinctive sexual dimorphism. Males are up to 30 centimeters taller than females and often twice as heavy. In addition to size and weight differences, males are distinguished by their striking silvery-gray fur, which forms a long mane covering their head, shoulders, and upper back like a cloak. Females, on the other hand, have shorter, brownish fur. Male baboons also have much longer canine teeth than their female counterparts. Both sexes have prominently red skin on their buttocks.

Habitat and Lifestyle

Hamadryas baboons inhabit savannas, steppes, rocky deserts, alpine grasslands up to 2,600 meters in elevation, and wooded areas in the Horn of Africa and Arabia. They depend on water sources and are therefore never far from water. These baboons are primarily terrestrial and move on all fours. At night, they retreat to rocky areas with cliffs, where they find suitable sleeping spots. During their daily search for food, they may cover up to 20 kilometers. Their home ranges span 10 to 40 square kilometers and often overlap with those of other groups.

Social Behavior and Reproduction

Hamadryas baboons have a multi-level social structure. The smallest social unit is the one-male unit (OMU), which can consist of up to 15 individuals. An alpha male lives with several females, their offspring, and a few younger males. The alpha male leads the group and is the only adult male with whom the females mate. He closely guards his females, sometimes aggressively, to prevent them from interacting with other males. As a result, the females tend to stay near the alpha male and give him the most attention, primarily through social grooming. Two or three OMUs together form a clan, where males are often related. Members of a clan forage together and engage in social interactions. Multiple clans form a larger group called a band, which can consist of up to 100 animals. Bands share home ranges and move together. At sleeping sites, several bands may gather in close proximity, forming what is known as a herd
Female Hamadryas baboons reach sexual maturity between four and five years, while males mature later, between six and nine years. Mating and births occur throughout the year. During ovulation, the perineal region (area between the anus and genitals) of females becomes swollen and reddened, signaling to the male that the female is fertile. During this period, the alpha male usually mates exclusively with his females. After a gestation period of 165 to 184 days, the female gives birth to a single infant, which is born with black fur. The infant's fur color changes after three to six months to match that of the females. The mother initially carries the young on her belly, then on her back, and nurses it for eight to twelve months. While females are responsible for raising the young, males also interact with them, playing and sometimes carrying them for short distances. Both male and female juveniles typically leave their birth group before reaching sexual maturity.

Baboons in Research

Hamadryas baboons are significantly larger than other non-human primates used in biomedical research, making them particularly suited for cardiovascular studies. For example, artificial blood vessels were first tested in baboons. They are also a crucial model in transplantation medicine. Globally, many people are waiting for donor organs, and the availability of heart transplants, especially in Germany, is limited. One potential solution is xenotransplantation, where organs, such as pig hearts, are transplanted between species. These procedures are tested in baboons to study compatibility and potential rejection reactions.