Drill Monkeys

Drills are among Africa’s most endangered mammals, and are listed by the IUCN as the highest conservation priority of all African primates. They are semi-terrestrial monkeys, exhibiting extreme sexual dimorphism with males weighing up to 45 kg – three times the size of females. They are semi-nomadic seasonally and little is known of their behavior or ecology in the wild. Their closest relative is the mandrill Mandrillus sphinx, found from southern Cameroon through mainland Equatorial Guinea (Rio Muni), Gabon and into Congo.  The two species are allopatric across the Sanaga River.

On Bioko drills occur as unique subspecies Mandrillus leucophaeus poensis.

Drills are found only in Cross River State, Nigeria; southwestern Cameroon; and on Bioko Island, Equatorial Guinea. Their entire world range is less than 40,000 km2, smaller than Switzerland. 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, the highest population estimate is 8,000.

Drills have also been declining in zoos internationally.

Adult male and female with their year-old offspring.

Drills are fully protected by law in Nigeria and Cameroon and portions of their habitat are technically safeguarded, however little real protection exists for drills or other endangered species that share their habitat. Drills will only survive the present and into the long term by the grace of their human neighbors, and the will and commitment of their host governments to enforce existing laws. As habitats shrink and become increasingly fragmented, the interactive management of wild and captive populations may play a crucial role.

 Drill distribution is limited to fragmented habitat islands within the red lines shown on this map. 

We will soon be putting up much more information on this page about the species, so please stand by!