Drill (mammal)
The Drill is a primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

 of the family Cercopithecidae (Old-world Monkeys), closely related to the Baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...

s and even more closely to the Mandrill
The mandrill is a primate of the Old World monkey family, closely related to the baboons and even more closely to the drill. Both the mandrill and the drill were once classified as baboons in genus Papio, but recent research has determined they should be separated into their own genus, Mandrillus...



The Drill is a short-tailed monkey up to 70 cm long, similar in appearance to the mandrill, but lacks the bright blue and red on the face of that species. It has high sexual dimorphism in weight with males weighing up to 20 kg, the females up to 12.5 kg.

The body is overall a dark grey-brown. Mature males have a pink lower lip and white chin on a dark grey to black face with raised grooves on the nose. The rump is pink, mauve and blue. Female drills lack the pink chin.


A single dominant male leads a troop of around 20 females and is father to most of the young. This group of 20 may join others forming super groups of over 100 individuals. They are semi-nomadic seasonally, and will often rub their chests onto trees to mark their territory. They are semi-terrestrial, foraging mainly on the ground, but climbing trees to sleep at night. The females give birth to a single baby; female young remain in the troop, while male young move out to join other groups.

Longevity is up to 28 years.

The diet is primarily frugivorous, taking a wide range of fruit, but they also eat herbs, roots, eggs, insects, and occasionally small mammals.

Distribution and status

Drills are found only in Cross River State
Cross River State
Cross River State is a coastal state in southeastern Nigeria, bordering Cameroon to the east. Its capital is at Calabar, and it is named for the Cross River , which passes through the state...

 in Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

, southwestern Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...

 (south to the Sanaga River
Sanaga River
The Sanaga River is a river of South Province, Cameroon, Centre Province, Cameroon, and West Province, Cameroon. Its length is 890 kilometers.The Sanaga River forms a boundary between two tropical moist forest ecoregions...

), and on Bioko
Bioko is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea. It is the northernmost part of Equatorial Guinea with a population of 124,000 and an area of . It is volcanic with its highest peak the Pico Basile at .-Geography:Bioko has a total area of...

 Island, part of Equatorial Guinea
Equatorial Guinea
Equatorial Guinea, officially the Republic of Equatorial Guinea where the capital Malabo is situated.Annobón is the southernmost island of Equatorial Guinea and is situated just south of the equator. Bioko island is the northernmost point of Equatorial Guinea. Between the two islands and to the...

. It occurs in rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...

 habitats. Their entire world range is less than 40,000 km2.

Drills are among Africa’s most endangered mammals, and are listed by the IUCN as the highest conservation priority of all African primates. Drill numbers have been declining in all known habitat areas for decades as a result of illegal commercial hunting, habitat destruction, and human development; as few as 3,000 drills may remain in the wild, with the highest population estimate only 8,000. A total of 174 drills recovered from illegal capture are in semi-captivity at the Drill Rehabilitation and Breeding Centre in Nigeria, with high success rates in breeding recorded there, and about 40 in other zoos internationally.

Two subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 of drill are accepted by some authorities, but are not considered distinct by others:
  • Mainland drill
    Mainland Drill
    The mainland drill is a subspecies of the endangered drill. It is distinguished by ringed yellow and black coloring on its crown, and is otherwise similar to the Bioko drill....

    , Mandrillus leucophaeus leucophaeus
  • Bioko drill
    Bioko Drill
    The Bioko drill is a subspecies of the endangered drill living on the island of Bioko in Equatorial Guinea. It is distinguished by a brownish yellow crown with a black tip. It is otherwise like the mainland drill....

    , Mandrillus leucophaeus poensis

Their closest relative is the mandrill (Mandrillus sphinx), found from southern Cameroon through mainland Equatorial Guinea
Equatorial Guinea
Equatorial Guinea, officially the Republic of Equatorial Guinea where the capital Malabo is situated.Annobón is the southernmost island of Equatorial Guinea and is situated just south of the equator. Bioko island is the northernmost point of Equatorial Guinea. Between the two islands and to the...

 (Rio Muni), Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...

 and into Congo. The two species are allopatric
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...

across the Sanaga River.

External links

  • Pandrillus - Drill and primate conservation group operating in Nigeria and Cameroon
  • The Limbe Wildlife Centre (LWC) - A wildlife rescue and rehabilitation project situated in the South West Region of Cameroon.
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