page_title: Mandrill
section_title: Social behavior and reproduction
hierarchical_section_title: Mandrill / Social behavior and reproduction
caption_attribution_description: Mandrill, Mandrillus sphinx, Zoo Augsburg
context_page_description: The mandrill is a primate of the Old World monkey family. It is one of two species assigned to the genus Mandrillus, along with the drill. Both the mandrill and the drill were once classified as baboons in the genus Papio, but they now have their own genus, Mandrillus. Although they look superficially like baboons, they are more closely related to Cercocebus mangabeys. Mandrills are found in southern Cameroon, Gabon, Equatorial Guinea, and Congo. Mandrills mostly live in tropical rainforest and in very large groups. Mandrills have an omnivorous diet consisting mostly of fruits and insects. Their mating season peaks in July to September, with a corresponding birth peak in December to April.
  Mandrills are the world's largest monkeys. The mandrill is classified as vulnerable by IUCN.
context_section_description: Mandrills seem to live in very large, stable groups named 'hordes'. A horde can number in the hundreds of mandrills, possibly averaging around 615 individuals and reaching as many as 845. It is difficult to accurately estimate horde size in the forest, but filming a horde crossing a gap between two forest patches or crossing a road is a reliable way of estimating the total number. The largest horde verifiably observed in this way contained over 1,300 individuals, in Lopé National Park, Gabon—the largest aggregation of nonhuman primates ever recorded. In the wild, males disperse and only female mandrills remain in their birth group. This benefits females to establish strong relationships with their relatives which can provide support during conflicts, better offspring and longer lifespan. These hordes are made of adult females and their dependent offspring. Males live a solitary lifestyle, and enter hordes only when females are receptive to mating, which lasts three months each year. All-male bachelor groups are not known to exist.
  The mating season of the mandrill takes place from June to October, which is when the sexual swellings of the female occur. They breed every two years. When breeding, a male will follow and guard a female in estrus. Adult males exist in two different forms: the brightly colored and "fatted" dominant males, and the paler and "nonfatted" subordinate males. Both males engage in mating, but only the dominant males can sire offspring. Males sometimes fight for breeding rights which results in dominance. Though conflicts are rare, they can be deadly. Gaining dominance, that is becoming the alpha male, results in an "increased testicular volume, reddening of sexual skin on the face and genitalia, and heightened secretion of the sternal cutaneous gland". When a male loses dominance or its alpha status, the reverse happens, although the blue ridges remain brightened. There is also a fall in its reproductive success. This effect is gradual and takes place over a few years. When subordinates mate-guard a female, the competition between them allows the dominant males to have a greater chance of siring offspring, since subordinates outnumber dominants 21 to 1. There is also a dominance hierarchy among females, with reproductive success being displayed in shorter interbirth intervals amongst these alpha figures and the beginning of reproduction at earlier ages.
  Mandrill births occur from January to May. Most births in Gabon occur in the wet season, from January to March, and gestation usually lasts 175 days. In captivity, 405 days separate each birth. Young are born with a black natal coat and pink skin. The females do most of the raising of the young. Alloparenting exists in this species, with female relatives providing care for the young. Males leave their natal groups when they are six years old and stay along the boundary of the social group.
  Mandrills will make a "silent, bared-teeth face", in which the teeth are bared, the head crest is erect and the head shakes. This may serve as a peaceful form of communication. A mandrill submits by presenting its rump. With aggression, mandrills will stare, bob their heads, and slap the ground. Vocalizations like roars, crowings, and "two-phase grunts" are made for long distances, while "yaks", grunts, "k-alarms", "k-sounds", screams, girneys, and grinds are made at short distances.
caption: At Augsburg Zoo, Augsburg
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