DRILLS and MANDRILLS
Colourful nose : The Mandrill (left) is the most colourful mammal and is more colourful than the drill (right). Both have colourful rear ends in hues from deep scarlet, reds and pinks to blue and a delicate lilac.
In the male drill, the face and muzzle are black, with red bands on the lower lip. Drills are dark brown with a black face, white tufted beard and scarlet lower lip.
The male mandrill goes one further and replicates his red and lilac genitals on his face. He has a bright red nose with bright blue bony ridges on either side. This mimics a snarl and the brightness and size of these ridges indicates the male's age and condition. The whole is framed with bright orange chin and side-whiskers. His colours brighten when he is excited: becoming bluer on his rump and chest, and red dots may appear on wrist and ankles! The female has smaller nose ridges and a grey-black face.
Why the colourful face? Males usually make up only 7% of the population, suggesting fierce competition among the males for breeding positions. In this competition, males gain advantage in prominently advertising his social position and readiness to mate. This may also explain why males are more than twice the size of females. Males also have larger canines. The males only colour up when they reach maturity.
They move on all fours when foraging. They are active during the day, starting off at dawn. They may rest during the day in between foraging sprees. Although they forage on the ground, all climb trees for safety when threatened by predators, and sleep in trees at night.
A parade of drills and mandrills*: Mandrills and drills live in harems which average 20-25, with one male and 5-10 females, the rest being juveniles. They break up into harems to forage during the peak of the fruiting season. When this ends and they are forced to turn to less nutritious but widely available food, 6-7 harems may join up to form larger feeding groups of 200-600. Small groups are quieter, while larger bands are very noisy. The dominant male decides where the group should forage, and directs them from behind. But if there is danger, he moves to the front. Some harems may include 2 or more subordinate males. These are duller in colour and are slimmer. The presence of the dominant appears to suppress the maturity of sons. Males rarely live alone, these are usually older individuals, probably ousted from their harems.
They are built not to jump agilely in trees but to maneuver and fight. Their faces are long, with doglike muzzles and heavy ridges of bone over the eyes. Their trunks are thick, their shoulders heavily muscled and made to appear even more formidable by a thick ruff of hair. They are clumsy in the trees, and leaping long distances from one tree to another would be impossible for them. And as for their temperaments, they can be tough, aggressive, even bellicose, prepared if necessary to stay and fight against all comers except lions, leopards and armed men.
Among the characteristic features of baboons (and some other Old World monkeys) are the tough, callous pads on the rump, adapted for the long periods of time when these monkeys sit or sleep on tree limbs. Called ischial callosities, these pads are attached directly to the undersides of the haunch bones. Hence there are no nerves or blood vessels to be pinched, and a monkey's legs do not "go to sleep" when the pressure of the body bears down on the pads. The most remarkable ischial callosities can be demonstrated by the sacred baboons females, their size and bright colour always attract attention
Mandrill talk: Drills are noisy, regularly grunting and screaming. Group members keep in contact with each other while foraging through loud conversations of grunting and crowing calls. They also alert each other of predators. A drill male's threat gesture is impressive including abruptly thrusting their head forwards, retracting their eyelids, puckering up their lips and raising the crest of fur on their heads. Both drill and mandrill males have chest glands which they regularly rub branches and tree trunks with. This scent helps to maintain the dominant male's aura.
Mating and babies: When the female is ready to mate, a marked swelling appears around her tail. The dominant male is the most likely to mate with her. Mandrill babies have a black coat and pink skin for the first 2 months.
Status and threats: CITES 1. Both drills and mandrills are better known in captivity than in the wild. There are about 3,000 left in the wild. The IUCN rated the drill as the highest priority among African primates. Drills are highly endangered because they are more localised, but mandrill populations have also suffered drastic declines. Both are severely hunted for their meat which is said to be sweet and is preferred over imported beef or mutton. Because they travel in large troops and are easily located by their constant grunting and screaming, entire populations are quickly decimated. Hunting has become lucrative and thus more efficient with the use of dogs, high-powered rifles, spotlights, deep-freezers and trucks. They are also killed as a pest on crops. In addition, they are severely affected by habitat loss due to logging and clearing for agriculture.
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Size: Head and body 61-76cm, tail vestigial 5-7cm. Male average 25 kg, female 11.5kg. Mandrill males can reach 54 kg.
Lifespan: Average 20 years in the wild, 46 years in captivity.
Babies: One young, twins rare. Gestation 168-178 days, maturity at 4 years.
Social life: Harems of 1 male and 5-10 females. 6-7 harems may combine to form troops of up to 200.
Distribution: Africa. The Mandrill is more widely distributed in Western Central Africa: Cameroon, Gabon and the Congo. The drill is only found in Cameroon, north of the Sanaga River and on the coastal island of Fernando Poo.
Habitat: Prefer dense rainforests near rivers, but are occasionally seen in young secondary growths. They avoid open areas.