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Drill: Characteristics, Diet, Facts & More [Fact Sheet]

The drill, a lesser-known yet fascinating primate, is one of Africa’s most endangered mammals. Resembling baboons in appearance, drills are unique in their behavior, ecology, and the challenges they face.

This article aims to shed light on these remarkable creatures, offering a comprehensive overview of their classification, physical traits, habitats, behaviors, and conservation status. By understanding more about the drill, we can appreciate its importance in the ecosystem and the urgency of its conservation.

The Drill at a Glance


Class:Mammalia (Mammals)
Species:M. leucophaeus

Essential Information

Average Size:Height: 18 to 30 inches (45.7 to 76.2 cm) at the shoulder
Average Weight:Males: 33 to 50 lbs (15 to 23 kg); Females: 24 to 29 lbs (11 to 13 kg)
Average Lifespan:Up to 20 years in the wild, up to 30 years in captivity
Geographical Range:Small parts of western Africa, primarily in Cameroon, Nigeria, and Bioko Island.
Conservation Status:Endangered (IUCN Red List)

Species and Subspecies

The drill is a single species, Mandrillus leucophaeus, with no recognized subspecies. They are closely related to the mandrill (Mandrillus sphinx), with some earlier classifications having considered them to be a single species.

The primary distinctions between drills and mandrills lie in their coloration and size, with mandrills being more vibrant and slightly larger.

  • Similarities with Mandrills: Both species are known for their striking facial coloration and pronounced sexual dimorphism.
  • Differences from Mandrills: Drills have less pronounced coloration, with males exhibiting a black face with a reddish lower lip and ridged nose. They are also generally smaller and less brightly colored than mandrills.

Understanding the drill’s unique identity is crucial for its conservation, as it faces different environmental pressures and threats compared to its more colorful cousin, the mandrill.

Group of drillsSource: Wikimedia Commons


Drills are robust primates with a sturdy build. They have a short tail, almost inconspicuous, and their coat is primarily olive-brown, with a darker back and lighter underparts. Adult males are significantly larger and more colorful than females, exhibiting a unique and striking appearance.

Males can reach a shoulder height of about 30 inches (76.2 cm) and weigh up to 50 lbs (23 kg), whereas females are smaller, usually around 24 to 29 lbs (11 to 13 kg). Males have a distinctive black face with a reddish lower lip and a ridged nose, while females and juveniles are less vividly colored.

They have strong limbs and their hands and feet are adapted for quadrupedal movement. Their facial skin is hairless and shows increased coloration with age, especially in males.

Drills exhibit pronounced sexual dimorphism. Adult males are not only larger but also more colorful than females. This dimorphism extends to their facial features, with males displaying more pronounced ridges on their noses and more vibrant coloration around their lips and chin.

Habitat and Distribution

Drills are native to a small part of Western Africa. Their population is concentrated in the Cross River region between Cameroon and Nigeria, with a significant population also on Bioko Island. Their geographical range is limited and fragmented, contributing to their endangered status.

Drills prefer dense, primary rainforests and can also be found in secondary forests. They are rarely seen in open or fragmented habitats, relying heavily on the cover and resources provided by the forest.



Drills are primarily diurnal, spending most of their daytime foraging, socializing, and moving within their habitat. They are known for their shy and reclusive nature, preferring to avoid human contact.

Drills live in large social groups, typically comprising one dominant male, several females, and their offspring. Group sizes can vary, often containing up to 20 individuals, but in some cases, supergroups of over 100 drills have been observed.

Social hierarchies are prominent, especially among males, where the dominant male has exclusive breeding rights. Social grooming plays a significant role in maintaining bonds within the group.

Communication among drills includes a range of vocalizations, body postures, and facial expressions. They use different calls for alarm, mating, and coordination within the group.

As with many primates, facial expressions also are an important part of their social interaction, used to establish dominance, submission, and other social dynamics.

Diet and Feeding Behavior

Drills are primarily omnivorous, with a diet that reflects the availability of food sources in their rainforest habitat.

They consume a variety of fruits, nuts, seeds, roots, and leaves. Animal matter, including insects and small vertebrates, can also be part of their diet, though this is less common.

Drills forage on the ground or in trees, using their strong limbs and hands to manipulate and break open food. Their diet changes seasonally, depending on the availability of different fruits and other food sources in the forest.


While adult drills are large and robust, making them less vulnerable to predation, they still face threats from a few natural predators.

The main predators of drills include leopards and large birds of prey. Young and juvenile drills are more susceptible to predation due to their smaller size and lesser strength.

Their social structure plays a key role in predator avoidance, with group members alerting each other to potential threats. The dense forest habitat also provides cover and an escape route from predators.

Mother drill and babySource: Wikimedia Commons

Reproduction and Life Cycle

The reproductive behavior of drills is characterized by a polygynous mating system, where one dominant male mates with multiple females.

Mating typically occurs during the dry season. The dominant male in a group has exclusive breeding rights with the females. Courtship involves displays of dominance and strength by the male.

The gestation period for a drill is about 6 months. Females usually give birth to a single infant. Twins are rare. Newborn drills are cared for primarily by their mothers, with infants being highly dependent for the first few months.

The mother is responsible for the nurturing and protection of her offspring. Young drills stay with their mothers for several years, learning essential survival skills.

The social structure of drills, combined with their reproductive strategy, plays a critical role in maintaining the stability and hierarchy of their groups, which is crucial for their survival in the wild.

Conservation and Threats

The drill (Mandrillus leucophaeus) is currently classified as endangered. This status is primarily due to their limited range and declining population numbers.

The most significant threat to drills is the loss of their natural habitat due to logging, agricultural expansion, and human settlement. They are also threatened by hunting for bushmeat, which is prevalent in some parts of their range. On top of that, habitat fragmentation further isolates populations, making them more vulnerable to extinction.

Conservation efforts for the drill include:

  • Habitat Protection: Preserving and restoring rainforest habitats.
  • Anti-Poaching Measures: Implementing and enforcing anti-poaching laws.
  • Public Awareness: Educating local communities about the importance of drills and the need to protect them.
  • Research and Monitoring: Ongoing research to better understand their ecology and behavior, and monitoring populations to track their status.

Fun Facts

  1. Impressive Size: Drills are one of the largest monkey species in Africa, with males being particularly robust and muscular.
  2. Colorful Displays: Male drills exhibit impressive coloration, with their faces and rumps showing bright colors that become more pronounced during the breeding season.
  3. Shy Nature: Despite their size, drills are known for their shy and reclusive behavior, often avoiding contact with humans.
  4. Social Complexity: Drills have complex social structures, with large groups often led by a single dominant male, demonstrating intricate social dynamics.
  5. Longevity: In captivity, drills can live up to 30 years, which is significantly longer than their average lifespan in the wild.

Frequently Asked Questions

How big do drills get?

Adult male drills can reach up to 50 lbs (23 kg) in weight and 30 inches (76.2 cm) in shoulder height, making them one of the largest monkey species in Africa.

Where can drills be found in the wild?

Drills are native to a small part of Western Africa, primarily in the rainforests of Cameroon, Nigeria, and Bioko Island.

Are drills endangered?

Yes, drills are classified as endangered due to habitat loss, hunting, and population fragmentation.

What do drills eat?

Drills are omnivorous, primarily eating fruits, nuts, seeds, and roots, but they also consume insects and small vertebrates occasionally.

How do drills communicate?

Communication among drills includes vocalizations for different situations, body postures, and facial expressions to convey social information within their groups.

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