They have also been known to form larger aggregations of these male dominated subgroups, totalling up to 200 individuals. 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. Habitat 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. 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.