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The Olé River meanders and falls through the Gran Caldera—a volcanic crater formed millennia ago, now dense with forest.

Island Ark: a threatened African treasure

On West Africa’s stunningly diverse Bioko Island, rare primates are being slaughtered to feed a growing bush-meat trade. When a team of photographers and conservationists documented the island’s biodiversity in January, they found that Bioko’s forests remain healthy, but its extraordinary animal life may not survive.

This story appears in the August 2008 issue of National Geographic magazine.
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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 ecosystem where life blooms from canopy to soil.

In the year 1551 a strange male animal was put on public display in Augsburg, Germany. He had humanlike fingers on his hands and feet, observers noted, and a “cheerful nature,” although he also had a tendency to turn his backside to viewers. Based on an illustration of the creature, biologists think it was most likely a drill (Mandrillus leucophaeus), a baboonlike primate. 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, they collectively gasped, then sat down on the rain forest floor to watch.

The drills, the largest primates on Bioko, were climbing and feeding in a fig tree at the floor of the island’s 7,000-foot-high Gran Caldera. Earlier that morning the scientists had spotted troops (each five to thirty strong) of chattering monkeys: red-eared, black colobus, and red colobus, the latter one of the most threatened of all primates.

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Hunting by night, a house-cat-size linsang prowls into a camera trap for a portrait.

Biologists regard Bioko Island as a living laboratory for studying how plants and animals evolve in isolation. It lies in the Gulf of Guinea, 20 miles off the west coast of Africa, one of four islands in an archipelago. The three others—São Tomé, Príncipe, and Annobón—are deepwater isles formed tens of millions of years ago and colonized by plants and animals from Africa that arrived on their shores by chance.

Bioko, however, was connected to the African mainland during each ice age, most recently about 12,000 years ago. Like an exclusive ark, the island shelters an isolated set of sub-species evolved separately from those on the mainland. There are seven species of monkeys, including the drills; four galagos (bush babies); two small antelopes (duikers); one species of porcupine; one species of tree hyrax; one species of pouched rat; and three species of scaly-tailed squirrels. There are catlike linsangs (but no lions or leopards). The roster once included forest buffalo, but they were hunted to extinction a century ago.

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Twenty miles of ocean, rocky headlands, and boat-beating surf—like that pounding Point Dolores here on the southern coast—have helped keep Bioko wild. Most of the island’s estimated 150,000 people live in Equatorial Guinea’s capital city, Malabo, in the far north.

Add orchids, land snails, freshwater fish, amphibians, spiders, and insects—all evolving apart from their mainland relatives. In the island’s interior, woodlands, grasslands, and rain forest remain much as they were when the first Portuguese explorers stepped ashore in the 15th century: largely untouched and beautiful.

“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 main-land 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.

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.”

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Chained to a post in Malabo, where the bush-meat trade thrives, this orphaned drill may be sold as a pet, or become dinner for its captors. Bioko’s drill population shrank by a third from 1986 to 2006.

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.

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Shoppers spend over $200 for a large male drill at the Malabo market, paying extra to have the fur singed off on-site. Chicken and other protein sources are readily available, and far cheaper than bush meat.

Documenting the carnage has had some effect. In October 2007 the BBPP convinced Equatorial Guinea’s president, Teodoro Obiang Nguema Mbasogo, to issue a ban against the hunting, selling, and consumption of primate meat. It had been in place for two months when the BBPP team arrived in January. How were the monkeys faring? And how would they react to humans who wanted to count rather than shoot them? It didn’t take long for the biologists to find out.

It was dusk, a time when monkeys chatter as they settle in for the night, but the caldera forest was oddly quiet. Butynski had anticipated an especially lively chorus because all seven monkey species live in the caldera. But there was little to hear aside from the trilling hum of insects and frogs. Butynski kept to a trail, stopping every 50 feet or so to look and listen. “Well,” he said at last, clearly baffled, “maybe the monkeys have moved to another part of the forest for the night.”

No sooner had he finished speaking than two fur bombs the size of large dogs hurtled overhead. They splashed into the leafy crown of a nearby tree and then plunged into another, as if diving from one green pool to the next. Finally, having uttered not a single call, they disappeared over the edge of a river gorge and into the forested twilight.

Butynski, who has made dozens of primate surveys throughout Africa, pulled out his notebook to record the sighting. “That’s a surprise—two drills,” he said. “They must have been in the trees sleeping when they heard my voice.”

The next morning Butynski set out into the caldera again. The instant he spotted a troop of red-eared monkeys, they began to give hack calls and chirps, eyes wide with terror. Mothers clutched babies to their breasts; branches bounced and limbs heaved as the monkeys scurried to get away.

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A thickly fruited fig tree provides nourishment for a Martin’s putty-nosed monkey. The rainy season lasts nearly all year in Bioko’s south; more than 400 inches of annual rainfall in some spots help a diverse garden grow.

Such fleeting glimpses were all the scientists came to expect. In the first three days of the survey, as the team hiked from the island’s southern shore 2,000 feet up the caldera, all the monkeys they spotted gave alarm calls before vanishing into one of the steep river gorges that cut through the caldera.

On the fourth day, however, the monkeys were less afraid. After hiking up and down steep, muddy trails littered with rough lava cobbles, the team reached the caldera’s northern end, its inner sanctum. Bioko receives more than 400 inches of rain a year, and although this was supposed to be the dry season, daily thunderstorms unleashed torrents. Between storms, the sun shone fierce and bright, and large beads of sweat rolled off everyone’s foreheads and noses.

Despite increased hunting, the forest canopy in this distant part of the crater fairly exploded with monkeys. In their leafy shelter a dozen red-eared monkeys leaped in alarm, trailing their long copper-colored tails along the branches and shouting their nasal call of warning. Forty feet farther on, a smaller group of gnomelike black colobus interrupted their leaf breakfast to race away. Just beyond them, a single charcoal-colored Preuss’s monkey jumped from a low bush where he’d been feeding into a towering mahogany tree, then leaped into a neighboring tree, his dark tail curled in a shepherd’s crook over his back. In the distance troops of red colobus gave honk calls, and crowned monkeys made their throaty booms.

Occasionally, red Ogilby’s and blue duikers crashed through the tangled undergrowth. Dozens of butterflies in brilliant hues and patterns to rival a Missoni gown flitted along the trail, while Jurassic Park–size earthworms and millipedes slithered into damp ravines, and pairs of gray parrots pirouetted in the sky.

Butynski jotted down each monkey troop and duiker, and stopped to inspect flowers, leaves, and fruits that monkeys had nibbled. Sometimes a strong, ammonia scent filled the air—the calling card of a troop of red colobus, one of the rarest of Bioko’s monkeys. But it was the drills—even scared drills—that we all most wanted to see.

Finally we spotted a small troop of drills below us on the far side of a river feeding in a tree. The distance and rushing water extinguished the sounds and smells of our little clutch of humans, and the drills went about their business as if we weren’t there. This was when we sat down to watch.

All had bushy, gray-brown pelts, and all but one were adult females or adolescents. The sole adult male was nearly twice as big as the others. He was simultaneously muscled and rotund, his Buddha belly at odds with his sharp-featured, obsidian black face. So sculpted were the angles of his cheeks, brows, and nose that he looked as if he wore a mask. White fur bristled around his face; his rump shone red, blue, and purple. Whenever he moved, the other drills got out of his way. At last, when they had eaten their fill, the troop clambered down the tree and vanished into the shadowy forest.

“Isn’t it remarkable?” Butynski said after the last drill was gone. For nearly 30 minutes the biologists had been able to observe monkeys that weren’t frightened of humans. “No one has studied the ecology and behavior of these animals in the wild,” he said. “But that might be possible here now: Someone could habituate a troop of drills to humans and start a long-term study.”

Even with the number of dead monkeys that the BBPP staff had counted in Malabo’s market, the northern caldera survey revealed a substantial and healthy primate population. “They’re certainly not naive anymore, and they’re not as abundant as in 1986, but they’re still in relatively good numbers,” Butynski said. His calculations suggested that the caldera’s forest shelters a little more than one monkey troop a kilometer. “It’s a much lower rate of encounter than what we recorded in 1986,” he noted. That year there were almost twice as many monkeys. Nevertheless, Butynski remains hopeful. “The forest is still intact, even in places where there aren’t monkeys now,” he said.

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A bush baby gazes from its sleeping tree with eyes that suit its nocturnal lifestyle. This one-pound primate subspecies is unique to Bioko. Hunters rarely take them, but biologists can’t ignore them. “They’ll sit on top of your tent and screech all night,” says Gail Hearn. Bats share the bush babies’ hours. Daylight brings out geckos, bugs, and blooms.

Intact habitat is key for Bioko’s monkeys. Most species go extinct for one of two reasons: overhunting or loss of habitat. It’s far easier to control the first problem, Butynski said, than to rectify the second. “Bioko is not like parts of East Africa, where people have cleared the forest to the mountaintops for agriculture. Even still, in East Africa people seldom hunt monkeys.”

“I’m an optimist,” he continued, taking a seat on a slope overlooking the caldera’s rugged rim and vine-draped woods. Recent monsoon winds and rainstorms had left parts of the forest flattened like wilted salad. Above the rumpled greenery, red-brown African mahogany trees rose at random, their trunks tall and straight, their limbs sagging with the weight of orchids and ferns. “Just look at those mahoganies. Anywhere else, they would have been logged long ago. This place is just too remote and difficult for large numbers of hunters to get to. It’s what keeps the monkeys relatively safe.”

Hearn, who hiked into the caldera a few days later, is not so sure. “We used to think the monkeys were safe here, that it was just too far for the hunters to travel. But it isn’t.”

On a camp table she unrolled a topographical map of the Gran Caldera and surrounding area. “See this area? It’s not that far from the northern edge of the crater.”

Hearn thinks the hunters probably use some of the trails the BBPP has cut over the years. “They know it’s a protected area, but there’s no law enforcement, so they come right in and shoot monkeys and duikers,” she said. “In the Malabo market they’ll even tell you brazenly, ‘It’s a Gran Caldera monkey.’  ”

For the first two months after the ban on primate meat was announced, monkey carcasses vanished from the market. You could still buy all the duikers, pangolins, pythons, pouched rats, and porcupines necessary to make a fancy stew—but not monkeys.

Part of the presidential edict explains that monkey meat is unsafe because “primates are carriers of epidemics and other pathologies” that can infect people. (Indeed, epidemiologists have found several simian immunodeficiency viruses in western and central Africa primate species, among which the precursors of HIV-1 and HIV-2 have been identified.) Hearn thinks the health risk may have discouraged the trade. “No one is going to serve their family meat that could make them sick,” she said.

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Slow to leap, and an easy target for poachers, the Pennant’s red colobus ranks among the world’s most endangered primates. Preserving its island sanctuary demands good science—and law enforcement.

Back in Malabo, Felix Elori, a former monkey hunter now employed in the oil industry, shook his head at Hearn’s suggestion. “Monkey meat is something we’ve eaten since we were young; it has a good flavor and isn’t bad for you,” he said. “It’s never made us sick.”

Elori doesn’t eat monkey meat himself, though. Two female drills he’d killed had had babies, a male and a female. He had nursed and raised them; now his sister keeps them in a cage. “I can’t eat monkeys anymore. They look like people. And anyway, it’s more economical to eat chicken.”

Did we want to buy the two young drills? he wondered.

Elori thinks the whopping fine—as much as a thousand dollars—is the best reason to forgo hunting monkeys. But after the two-month lull, the trade in monkey meat may be resuming. The day after Hearn and Butynski returned with the expedition to Malabo, a drill and two red colobus went up for sale. They’d probably been killed near the caldera.

Hearn’s face fell at the news. “It shows the ban alone is not enough. It’s going to take law enforcement and armed forest patrols,” she said. “At least they’ve taken the first step.”

If the hunting can be stopped for good, monkeys may return to all of Bioko’s forests. The caldera populations will serve as the source, Butynski says, and scientists, students, and the people of Bioko will have a rare chance to watch a natural experiment take place: monkeys reclaiming their ranges of old.

This research project was funded in part by your Society membership.

Author Virginia Morell writes regularly about science and natural history. Christian Ziegler specializes in ecology and conservation of tropical rain forests. Joel Sartore and Tim Laman are veteran shooters for the Geographic; Ian Nichols is currently on assignment photographing chimpanzees in Congo.