 Lowland populations tend to be more diverse, potentially due to a higher diversity of vegetation, with fruits more prevalent at lower altitudes and higher altitudes more conducive to more fibrous sources of food such as herbs and ferns.There are also comparatively higher densities in populous reached to the south and east of the island, due to a relative lack of road infrastructure, and hunting out of drills in the northern parts of Bioko.The inaccessibility of these regions for hunters allows the drills to reach greater populations without hunting pressure.