 Hunting of the Bioko drill is banned in most areas of Bioko Island, as they predominantly inhabit protected areas on the island, however the ban is considered ineffective and hunting remains the largest threat to the drill's population.The Bioko drill is of a similar appearance to the mainland drill, with a green-brown coat and white fur on the underbelly.It is distinguished by a yellowish crown of fur with black tips that lines the drill’s face, while the mainland drills have a crown that is mostly white.