"It's as close to pristine as any place I've seen," said Gail Hearn, one of the researchers leading the expedition into the Gran Caldera—her 13th trip into its forested depths. A primatologist at Pennsylvania's Drexel University, Hearn made her first trip here in 1990, intending to start a long-term study of the Bioko Island drills. Instead, "I just fell in love with the whole place," she said. "We've done so much damage to this planet. Here it's undamaged and impossibly beautiful. It feels like a place where one person could make a difference."

Hearn organized the Bioko Biodiversity Protection Program (BBPP). Each January she brings together teams of scientists and American and Equatorial Guinean students for comprehensive biodiversity surveys. This year a team sponsored by National Geographic magazine, Conservation International, and the International League of Conservation Photographers joined her for a 12-day RAVE (Rapid Assessment Visual Expedition) to document as many monkeys as possible, along with the rest of Bioko's stunning variety of other species— a richness protected by the island's history but now threatened by rampant hunting.

Bioko's flora and fauna so impressed the first European visitor, 15th-century Portuguese explorer Fernão do Po, that he named the island Formosa, "beautiful." Europeans who followed wanted to plant their first African colony here.

The indigenous Bubi people, however, who had arrived from mainland Africa, refused to cooperate with the white-skinned arrivistes, scuttling every attempt at European settlement until 1827. That year Britain established a base at Malabo (now Equatorial Guinea's capital) to combat the West African slave trade. Spain, which later colonized the neighboring mainland region of Río Muni, ultimately gained control of both colonies. The two together, called Spanish Guinea, gained independence from Spain in 1968 and emerged as the Republic of Equatorial Guinea.

Settlers from the mainland belonging to the Fang ethnic group took control from the Bubi, and since the Spanish left, Bubi separatists have clashed often with government forces. Neither the Fang nor the Bubi locals, accustomed to hunting the island animals for food, share the scientists' appreciation of Bioko's unique biodiversity. Further thwarting conservation efforts is a burgeoning offshore oil industry. Vast stores of oil and natural gas were discovered in the last decades of the 1900s, and now American corporations are pumping some 400,000 barrels of oil and natural gas a day, bringing new wealth to the island. More and more people who love the taste of monkey meat have the cash to buy it.