Voice of a forest, the red-eared monkey is the most abundant of Bioko Island’s 11 primate species. At least 12,000 years of isolation from mainland Africa has helped produce a one-of-a-kind ...

Roughly 20 miles off the coast of west Africa sits a volcanic relic now completely blanketed in equatorial rainforest the island of Bioko Its home ... the most endangered primates in the world ...

Off the coast of Central Africa lies an isolated island ... this terra incognita is called BIOKO. The ruler of this realm is one of the world's least known primate species, the drill.