Primatologist Tom Butynski, senior conservation biologist on the expedition, first visited Bioko in 1986 in response to an International Union for Conservation of Nature report that identified the island as an important place to survey for monkeys. At the time, no biologist had visited for more than two decades, and Butynski expected to find the monkeys hunted nearly to extinction.

Instead, he found them thriving. It turned out that to prevent Bubi uprisings the Fang government had confiscated the islanders' shotguns from 1974 to 1986, which had given the primates a reprieve. Further, large tracts of lowland rain forest that the Spanish had cleared for cocoa plantations were returning to forest after the plantations were abandoned. Monkeys were busy recolonizing the forests.

"We saw about two troops a kilometer in the Gran Caldera transect," Butynski said. The monkeys were abundant, and they were fearless. "I remember thinking how naive they were. We were able to get good, close-up looks."

But there were ominous signs as well. During the same ten-week survey, Butynski spotted 14 Fang hunters with shotguns and saw numerous traps set for duikers, monkeys, and smaller mammals. Around the same time, bush-meat sales increased in Malabo. As in much of West Africa, bush meat, from wild animals in the forest, particularly from monkeys, is prized as a delicacy, even though it costs much more than chicken in local markets.

The steady slaughter of monkeys has taken its toll. By the time of this year's BBPP survey, hunters had wiped out many of the monkeys at the northern end of the 780-square-mile island, including those in a national park. They had also started shooting the monkeys in the Gran Caldera and Southern Highlands Scientific Reserve at the south end of the island, where villagers aided by the BBPP monitor monkey numbers.

Over the past decade BBPP staff have recorded the number of monkeys in the meat markets, and the tally had reached more than 20,000 by the end of March 2008. Tens of thousands of other animals have ended up there too. It is clear that all seven monkey species are in danger of becoming extinct, and that the Equatorial Guineans could well eat their way through the island's fabled biodiversity.