The vivid coloration of their bottom is a result of blood vessels located there

The drill has a dark grey-brown coat and a short tail. Males can be easily distinguished from females as males are twice as large as females. Males also have a pink lower lip which is absent in females. Their rump is pink, mauve, and blue. Facial expression is a primary means of communication, such as exposing their teeth and displaying a ‘grin-like’ expression.

Generally, this is a friendly gesture; however, they can also use it during conflicts.

They are classified as Endangered as their numbers have been declining for decades because of illegal habitat destruction, commercial hunting, and human development. Hunters can kill up to 20 drills per expedition.


Population est.
Equatorial Guinea

Did you know?

  • Drills are only found in Nigeria, SW Cameroon, and the island of Bioko; they were thought to be extinct in Nigeria and on Bioko island in the 1980s.
  • An oddly positioned crimson red line under their lower lip looks like misplaced lipstick.
  • Males with the brightest rumps have the highest rank! Their colorful rumps are said to be an indication of rank.
  • In contrast to other monkeys that only exhibit their “appeasement grin” in angry situations, drills utilize it mostly for greeting.
  • Drills walk on their hands and feet’s flat surfaces rather than their knuckles like apes do.
  • The drill monkey is one of the world’s least-known primates due to its low numbers and the difficulty of studying them in their small remote range habitat.
  • According to census estimates, there are just a few thousand drill monkeys left in the wild. Over the last 30 years, continuous threats have reduced the population by more than 50%-70%.
  • Drills are among Africa’s most endangered mammals, and the IUCN declared them to be the most endangered of all African primates.
  • Drills are very vocal, which allows groups to remain cohesive. They produce a lot of noise in the forest, which makes them an easy target for hunters.
  • As part of a conservation effort, an in-situ facility in Nigeria maintains a large, genetically diverse population; another captive population is kept in Cameroon.

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Terrestrial / Aquatic

Altricial / Precocial

Polygamous / Monogamous

Dimorphic (size) / Monomorphic

Active: Diurnal / Nocturnal

Social behavior: Solitary / Pack / Herd / Troop

Diet: Carnivore / Herbivore / Omnivore / Piscivorous / Insectivore

Migratory: Yes / No

Domesticated: Yes / No

Dangerous: Yes / No