Even today, more than 450 years later, drills are studied so infrequently in the wild that when a small team of biologists recently spotted a troop of them on Equatorial Guinea’s Bioko Island ...

Treading water and barely able to open my eyes in what felt like a constant driving rain, I craned my neck upwards trying to guess the height of the ledge above. I was under a cascade of water ...

The ruler of this realm is one of the world's least known primate species, the drill.