Mandrillus leucophaeus
drill

Drills are found only in Cameroon, north of the Sanaga river and on the coastal island of Fernando Poo. The largest protected population is found in the Korup National Park in the northern part of Cameroon.

Drills are found in the lowland forests, coastal, and riverine forests of western Africa. They prefer the habitat of mature forests, but have been seen on occasion in young secondary forests. Drills avoid open country away from the shelter of the forests. Males are mostly terrestrial, with smaller females and young ascending into the lower canopy to obtain both food and shelter.

Members of the genus Mandrillus meaure 610 to 764 mm in length, with the tail adding an additional 52 to 76 mm. Males are nearly twice the size of females, weighing in at an average 25 kg, compared to the diminuative females, which weigh only 11.5 kg on average.

Drills have distinct ridges on the side of their nasal bones, which are caused by outgrowth of the ridged and grooved bone. Male drills are easily distinguished from male mandrills by the absence of brightly colored facial skin, and the absence of prominent grooves in the facial ridges. The facial coloration of drills is jet black, except for the lower lip, which is bright red.

This genus is characterized by beards, crests, and manes. The pelage of drills is brown with a yellow tinge.

The skin on the rump of these animals is bright red, due to increased density of blood vessels in the region. The genitals of males may also be blue or violet. The rump coloration in females and juveniles is less pronounced.

The maximum reported lifespan for this genus is 46 years of age.

Little is known about the wild behavior of drills. In captivity, these monkeys form either one-male or multi-male groups consisting of between 20 to 25 individuals. They have also been known to form larger aggregations of these male dominated subgroups, totalling up to 200 individuals. Locomotion is quadrupedal.

Much of the communication among drills is visual, with displays of brightly colored posteriors and markings bordering their nasal passages. Drills are noisy creatures, regularly emitting grunts and screams, but the purpose of these sounds is not yet known.

In addition to these forms of communication, it is likely that tactile communication is important, both between mothers and their offspring, and between mates. Most primates spend significant amounts of time grooming their allys, and grooming can be used to maintain social bonding.

Both drills and mandrills possess scent glands on the chest which are used for marking branches. This scent marking is a form of chemical communication.

Drills are omnivorous creatures that rely on fruit, leaves and invertebrates (mainly termites) as food sources. They have been known to raid the manioc and palm oil plantations in search of food.

Predation on these animals probably occurs. Likely predators include leopards as well as other large carnivores.

To the extent that these animals serve as prey for carnivores, they may impact carnivore populations. It is likley that through their frugivory they play some role in seed dispersal.

Drills are viewed as crop pests and are often shot and killed by farmers.

These primates are hunted for meat.

Destruction of the mature forest in Cameroon is the primary factor in the decline of drills over the last twenty years. Unfortunately, the reforestation in these areas has concentrated on the planting of exotic, non-palatable species. Drills are also hunted extensively for their meat, which is considered sweet. Unfortunately, since drills form huge aggregations, hunters easily slaughter up to twenty individuals in one expedition.

It is essential that hunting and logging restrictions be placed in the areas where the drill lives or the species wil surely not survive. Cites Appendix I, Endangered