Photo courtesy of ARKive.org
Geographic Distribution and Habitat
- Drills are a type of forest baboon. They live in the forests of Africa in the areas of Cameroon and Nigeria and also the island of Bioko, Equatorial Guinea.
Size & weight
- Drills display very distinct sexual dimorphism. The males can grow double in size compared to females. Males grow to about 75 lbs (35 kg) where females are about 30lbs (14 kg). They average 22 in (56 cm) in length.
- Both males and females have an olive brown coat with a paler or white paler underbelly. Adult males and females show differing characteristics besides the obvious size difference. When males start becoming older they develop a colorful red chin. Their bottoms also become red, pink and blue. These colors become more vibrant as they get more excited. When females are ready to mate (in estrus) their genitals swell up, and their bottoms become a deep red when they become pregnant.
- Drills are most closely related to mandrills and baboons, which explains why they look similar to baboons with an extended nose and black face. And a short nub of a tail. They have very large canine teeth that are a very good defensive tool.
Behavior and lifestyle
- Drills are mainly frugivores, which means they mostly eat fruit. But fruit is sometimes hard to get so they will resort to plants, insects, eggs and small mammals as their fallback foods.
Behavior and lifestyle
- They are social animals, living in groups of about 20 individuals. This number can vary greatly depending on the group. There can be smaller groups while other groups consist of hundreds. These larger groups often break off into smaller ones when it is time to feed. This is referred to as fission-fusion societies because they break off and come back together at various times. Their social grouping is multi-male with multi-female, meaning that there is a mix of sexes within one group. There is one dominant male that rules the group. Males leave their natal group when they become sexually mature.
- Drills are diurnal, meaning that they are active during the day.
- A unique characteristic is that drills communicate a lot with their facial expressions. They open their mouths in a big wide grin. For most primate species this is a threat saying, "back off I'm getting mad.” But for the drill it is mainly used in a friendly sense. They communicate in other auditory ways as well.
- They are mostly terrestrial primates, walking on all four limbs on the ground, but they sleep in the lower canopy of the trees at night away from predators.
Conservation Status and Threats
- The Drills are very endangered and continue to dwindle in numbers. The entire space that all drills inhabit is smaller than the state of West Virginia.
- The decline in Drill population is due to illegal commercial hunting, habitat destruction and fragmentation, and human development. Less than 10,000 drills still live in the wild, and numbers may be as low as 4,000. Protection laws have been enacted in the small territory that they inhabit, but these laws can be difficult to regulate and enforce.
- For more conservation efforts, visit and watch the film at thedrillproject.org/the-drill. This project is a huge effort to help conserve the Drill populations so that this amazing primate will continue on successfully through future generations.
Video courtesy of ARKive.org
Written by Heidi Giancola, March 2016