Like all baboons, the hamadryas baboon is primarily terrestrial, but will sleep in trees or on cliffs at night (2) (6). An opportunistic feeder, it will take a wide variety of foods, including grass, fruit, roots and tubers, seeds, leaves, buds and insects (1) (2) (3) (6). Baboons may also hunt small mammals, including hares and young gazelles (3) (6). The female hamadryas baboon usually gives birth to a single young, after a gestation period of 170 to 173 days (2). Breeding may take place at any time of year, but births typically peak between May and July or November and December in Ethiopia (2) (5), and each female usually only gives birth once every 15 to 24 months (3) (9). The newborn hamadryas baboon has black fur and pink skin (3), and is suckled for up to 15 months (2). Lifespan in captivity has been recorded at 37 years (2).
The social system of the hamadryas baboon is intriguing in its complexity and its unique levels of organisation. Each adult male controls a small group of females (a harem) and their young, and remains bonded with the same females over several years, aggressively ‘herding’ any that wander, and retaining exclusive mating rights over the group. The females will often compete to groom and stay close to the male, and it is the male who dictates the group’s movements. Solitary males may sometimes follow the group. Males from a number of these family units often cooperate and interact, and may be closely related, forming associations known as ‘clans’. At the next level of organisation, several one-male units regularly interact in ‘bands’ of about 30 to 90 individuals, and a number of bands often share the same sleeping site, forming a ‘troop’ of up to several hundred individuals (2) (3) (6) (10) (11). Young males adopt a number of strategies to obtain females, including luring or abducting a juvenile female from a group, and guarding her until she is old enough to breed (3) (5) (11). While male hamadryas baboons typically remain in the natal clan for life, young females may transfer between clans or even bands (3) (9) (11).