This article appears in the April 2017 issue of National Geographic magazine.

It’s daybreak at 11,000 feet, and somewhere below, the monkeys are stirring.

Admassu Getaneh marches past flowering herbs and thick grass along the edge of a plateau in the central Ethiopian Highlands. Morning sun glints off his Kalashnikov rifle. At his feet basalt pillars plunge down to East Africa’s Great Rift Valley. Soon an unearthly screeching will begin as hundreds of primates awaken from their nightly cliffside slumber and vault onto the plateau like an army of furry circus performers. But Getaneh isn’t here to see that.

Short and slight in camouflage gear, Getaneh turns his back to the escarpment. He raises his binoculars. “I can see all the action this way,” he explains. Theropithecus gelada, sometimes called the bleeding heart monkey, may not draw Getaneh’s attention. But his presence helps explain why geladas here thrive.

View Images A gelada leaps over a small runoff stream as an infant (obscured except for its tail) clings to her back. Geladas live only in Ethiopia, but their now extinct relatives once inhabited lands from South Africa to southern Europe and as far east as India.

On and off for nearly half a millennium, rural enforcers have done what he’s doing today: patrolling the perimeter of a 42-square-mile high savanna called the Menz-Guassa Community Conservation Area, or simply, Guassa. Getaneh, a hired gun and former soldier, is here to make sure that no one steals or ruins the grass.

If you want to protect the world’s only grass-eating monkey, saving the grass is a good start. But Getaneh’s forebears weren’t in it for geladas. They were trying to save themselves. Native vegetation is everything in the highlands. Slender, sturdy stalks get strung into thatch and used for roofs. Men braid grass into rope. Women and children tie blades, sheaths, and stems into brooms and torches. Grass gets stuffed into mattresses. The prickly shafts even drive off fleas.

View Images Male geladas’ outsize canines aren’t used for hunting. Instead they’re used when fighting, threatening other males, or defending themselves against predators. Geladas’ specialized molars are unlike those of other living primates and help the monkeys grind grass.

Yet across the misty highlands, where about 80 percent of Ethiopians live, grasslands, meadows, thickets, moors, and swamps are deteriorating into rock and dead earth. The population is exploding. (Home to an estimated 100 million people, Ethiopia, after Nigeria, is Africa’s second most populated nation.) Farms sprawl across damp, rich land, displacing native plants that help the ground hold moisture. Erosion wipes out 1.5 billion tons of topsoil annually, pushing subsistence farmers to even more marginal ground. Farm animals trample soil, and with 49 million cows and 47 million sheep and goats, Ethiopia has more livestock than any other African country. That upends a delicate balance between native flora and rodents, reducing food for everything from Abyssinian hares to wattled ibises.

This pattern plays out across Ethiopia—almost everywhere, it seems, except here. In Guassa the grass is high and wavy, the torch lilies and giant lobelia left to grow for years. It’s not a park. Local villagers run this place. A complex communal system determines where livestock grazes, who cuts grass, and when. As a result this landscape one-sixth the size of Nairobi is among East Africa’s healthiest. Nearly a quarter of the country’s endemic mammal species live here. There are about two dozen of one of the world’s most endangered canids, the ginger-furred Ethiopian wolf. Guassa is a hot spot for klipspringers, civets, African wolves, and hyenas. And unlike elsewhere in Ethiopia, its 800 or so chattering geladas live much as they have for thousands of years.

View Images Geladas eat well in the Menz-Guassa Community Conservation Area because the vegetation is diverse. Admassu Getaneh, a former soldier who manages the area, known as Guassa, patrols for farmers illegally grazing their livestock or for poachers harvesting grass.

This small but spectacular wildlife success story is, in other words, a happy accident. I came to Ethiopia to see whether Guassa could serve as a model for conservation. What I found was a region changing so quickly that I had to wonder, Can Guassa’s monkeys and farmers navigate the pressures to come?

Weeks before meeting Getaneh, we fled the crowds and dust of the capital, Addis Ababa, and corkscrewed into the clouds toward Guassa. Scientist and photographer Jeffrey Kerby and I passed dry farms and rock huts. We saw women trailing donkeys stacked with hay. Men prodded goats with long staffs. Ethiopia may evoke images of camels and harsh salt pans, but it’s mostly mountains. The first trickles of the Blue Nile start in the highlands. We were headed to Africa’s roof, where Kerby is part of a decade-long gelada research project founded and run by Peter Fashing and Nga Nguyen, anthropologists at California State University, Fullerton.

Highland refuge Living at high, harsh elevations shielded geladas from competitors as a shifting climate drove other Pleistocene grass-eaters to extinction. Simien Mts. National Park Sudan Red Sea Eritrea Mekele Yemen Gonder ETHIOPIA Lake Tana Djibouti Bahir Dar Ethiopian Highlands Menz-Guassa Community Conservation Area Debre Birhan Addis Ababa AFRICA Asela MAP AREA Gelada range Ethiopia 300 mi 300 km Highland refuge Living at high, harsh elevations shielded geladas from competitors as a shifting climate drove other Pleistocene grass-eaters to extinction. Simien Mts. National Park Ethiopia Red Sea Sudan Mekele Eritrea Ethiopia Yemen Ras Dejen 14,928 ft 4,550 m Gonder ETHIOPIA Lake Tana Bahir Dar Djibouti Ethiopian Highlands Dessie Menz-Guassa Community Conservation Area Mehal Meda Debre Birhan Addis Ababa AFRICA AREA ENLARGED Asela Ethiopia Gelada range 300 mi 300 km Lauren C. Tierney, NGM Staff; Tony Schick<br>Sources: Ryan J. Burke, University of Oxford; Jeffrey Kerby, Dartmouth College

We crested one last rise. The parched earth and trees gave way to a lush, vivid carpet of green. Almost immediately, our hosts appeared. Three scampering geladas crossed the road, the smallest doing rhythmic half cartwheels. One landed on a rock 10 feet away. His eyes clocked us as we passed. A hay-colored mane spilled down his shoulders. His arms and fists appeared stuffed in black evening gloves. He looked almost regal.

Survival of the Grass-Eaters The geladas of the Ethiopian Highlands are often mistaken for baboons but are actually the last members of their own genus, Theropithecus. The unique morphology, diet, and behavior of the world’s only grass-eating monkeys are helping scientists hunt for clues about primate evolution. closest living relatives Geladas (below, left) are similar to baboons, but with key evolutionary differences. Average length (male) 2 feet Gelada Olive baboon Grass-grinding teeth Geladas’ canines are for fighting and display, with smaller incisors and larger, serrated molars for grinding grass. Baboons are omnivores. Gripping hands Geladas’ longer, stronger thumbs and relatively shorter index fingers give them a pincerlike grip for pulling grass. Male olive baboon Male Gelada A male’s thick cape provides warmth and may attract females. Red chests Geladas’ red chest patches are unique among primates and are highly visible, even while they sit to forage— which is most of the time. Among male geladas, dominant individuals have the reddest coloring. Survival of the Grass-Eaters The geladas of the Ethiopian Highlands are often mistaken for baboons but are actually the last members of their own genus, Theropithecus. The unique morphology, diet, and behavior of the world’s only grass-eating monkeys are helping scientists hunt for clues about primate evolution. closest living relatives Geladas (below, left) are similar to baboons, but with key evolutionary differences. Male olive baboon Male Gelada Average length (male) 2 feet Gelada Olive baboon A male’s thick cape provides warmth and may attract females. Grass-grinding teeth Geladas’ canines are for fighting and display, with smaller incisors and larger, serrated molars for grinding grass. Baboons are omnivores. Red chests Geladas’ red chest patches are unique among primates and are highly visible, even while they sit to forage— which is most of the time. Among male geladas, dominant individuals have the reddest coloring. Gripping hands Geladas’ longer, stronger thumbs and relatively shorter index fingers give them a pincerlike grip for pulling grass. Manuel Canales, NGM Staff; Shizuka Aoki; Tony Schick<br>Sources: Vivek Venkataraman, Harvard University; Jeffrey Kerby, Dartmouth College; Peter Fashing and Nga Nguyen, CSU Fullerton; Biren Patel, University of Southern California

Geladas, one of the flagship species of Africa’s alpine grasslands, are found only in the Ethiopian Highlands. They are the smallest vestige of a genus that millions of years ago stretched from South Africa to Spain and into India. Once among the most prominent primates—one species was the size of a gorilla—they were likely driven to extinction by climate changes, competition with more adaptable baboons, and our ancestors, who butchered them. Today all that remains of Theropithecus are geladas, which offer valuable, if imperfect, insight into the world inhabited by our predecessors. There is no other animal like them.

Hours after arriving at the research camp—seven tents, a rarely used bucket shower, and a muddy tepee that serves as a guard shack—Kerby and I set off. We walked past a hidden camera trap. Sixty-five monkeys sat in a meadow. The air smelled of thyme. The monkeys didn’t look up as we waded through. A baby sprawled on its back, one adult grooming its face, another stroking its leg. “That kid’s getting the deluxe treatment,” Kerby joked.

A Day in the Life of a Monkey

Geladas’ most recognizable features are crimson patches of hairless skin on their chests. In females, this region changes color, and tiny sacs around its edge fill with fluid, often indicating that they are ready to mate. The pink on dominant males darkens to red. Other primates signal sexual readiness with their rumps, but these monkeys spend most of the day scooting on their rears, gorging. Most primates climb trees to eat fruit and leaves. Geladas use opposable thumbs to pluck grass blades and herbs. Like zebras, they mince food with their molars. In theory, Kerby said, “primates shouldn’t eat grass.” From a nutritional standpoint, grass holds little energy. Getting enough takes work and time. Such inefficiency would have made it hard to fuel the evolution of a big brain. That might explain why geladas are less curious than, say, Botswana’s chacma baboons when shown dolls or rubber balls. But that doesn’t mean these monkeys aren’t crafty.

Kerby and I squatted and listened. The air filled with squeaky chewing. One animal emitted a guttural seagull honk. I heard shrieks as if from squabbling crows. A female grunted “Uh, uh, uh,” which Kerby said roughly translates to “Yo dude, I’m right here.” Geladas form roving primate cities, arranging themselves in herds of several hundred. They communicate using one of the largest vocal repertoires of any nonhuman primate. Their lip-smacking “wobble” may even offer evidence that facial noises were a precursor to human speech. To document behavior and family dynamics, researchers give geladas memorable aliases. That can make life on the plateau seem at times like a daytime soap opera.

Tiny Astral, for example, is known for starting fights, swiping at larger monkeys, then ducking behind her mom, Autumn, like a spoiled mean girl. Lydia isn’t the best mother to Lobelia, so Lydia’s sister, Lox, often steps in. When Lydia abandons her offspring, which is often, Lox lets Lobelia hitch rides on her back. Five Dollar Footlong (named for a sandwich) once stood on hind legs with arms outstretched as if desperate for a hug. Instead, his mother, Frodo, slapped him.

Females form a sisterhood, moving in reproductive units with one or a few males. Geladas aren’t monogamous, so male-on-male encounters are often fraught. Take Reverend Lovejoy. When this leader, named for a preacher on the television show The Simpsons, spied a rival’s infant in rich grass, he screamed. He flapped his eyelids and flipped up his lips. He bared impressive daggerlike canines. Geladas don’t use these teeth for hunting. They’re for display and fighting. Reverend Lovejoy raced to scare the youngster, but then his rival swooped in. They faced off, inches apart, huffing, until the rival backed down.

Time-Lapse: Gelada Monkeys in the Ethiopian Highlands

Guassa researchers, from Ethiopia and abroad, have followed the minutiae of the daily life of almost 500 individuals. They monitor activity, study relationships, track births, and document deaths. While studying responses to dying, they watched an infant, Tussock, cry alone beside her dead mother, Tesla, as the herd disappeared into the distance. They’ve solved riddles. Though geladas bolt or freeze when most carnivores pass, these monkeys seem unfazed by wolves. Rather than scaring the herd by picking off baby geladas, wolves have learned that the monkeys flush out rodents, and the wolves actually get more to eat.

Yet much about geladas remains unknown. After a revolt in Ethiopia ousted Emperor Haile Selassie in 1974, a civil war made fieldwork difficult. In the early 1990s uprisings drove out the ruling communist junta, the Derg, and scientists returned. Today it’s still not clear how many geladas are left. A few hundred thousand? Tens of thousands? Most of the country’s terrain has been converted to agriculture. There are simply too many farms, too much erosion, to support a rich array of grasses. Gelada numbers are high in the Simien Mountains, but that northern region is overrun by livestock. Many natural predators there are gone. Throughout the highlands, scientists have found small populations of monkeys surviving even when hemmed in by farms. But for how long?

Guassa is different. Carnivores abound. Geladas’ diets are typically 90 percent grass, but here they eat more than 60 types of plants, so grass makes up just over half of what they eat, likely paralleling the diet of some early hominins. Theropithecus is helping scientists learn how human ancestor Paranthropus boisei, once erroneously known as Nutcracker Man, may have thrived on similar vegetation. “Studying gels here isn’t like studying them in other places,” Kerby said. “This place is a window into a bygone era. And there are only so many time machines left.” Guassa just managed to get things right.

Getaneh fixes me with a patient, crooked smile. He, Kerby, and I are on patrol. Yo-yoing up small buttes. Hiking through underbrush. Looking for thieves. We have to keep moving. We have 12 miles to cover.

Getaneh runs Guassa’s conservation office. He protects it from those who’d bring harm. No one lives in Guassa, but 45,000 villagers pack its outskirts. Residents plant barley, lentils, potatoes, and sometimes wheat. They raise cows and sheep and burn livestock dung to cook distinctive Ethiopian flatbread, called injera. Small farm groups, called kebeles, elect representatives to oversee the landscape. Managers close rangeland for months or years until Festuca—the grass for which Guassa is named—is flush and ready for cutting. That doesn’t stop everyone. Thieves with hand scythes dart across hills, illegally swiping grass to sell as far away as Debre Birhan. Poachers dig out the roots of flowering plants for firewood. Getaneh sometimes tracks outlaws with teams of scouts. Often the scouts patrol without him. When Getaneh is alone, he relies on stealth. He is a furious ghost.

View Images A male gelada walks through torch lilies that carpet Guassa’s alpine slopes on a cool, foggy day.

Guassa’s land-use ethic is steeped in legend and in the church. In the late 1600s, according to oral histories, two Coptic Orthodox Christians, Asbo and Gera, stumbled onto Guassa. Both claimed its bounty. So the duo galloped their horses, dividing the land where the first steed fell. Communities split into parishes that answered to an elected leader who protected grass at all costs. Shared resources without strong management often fall victim to selfish acts by individuals. Peer pressure and association with the church seemed to help in Guassa. Preservation was an almost spiritual obligation. Villagers prided themselves on stewardship. Grazing seasons even ended on religious holidays. (“Usually when these types of common properties lean on sacred institutions, they become sacred themselves,” pointed out Ethiopian scientist Zelealem Tefera Ashenafi, a Guassa expert.) And when all else failed, there were men like Getaneh.

We sit while he recounts a story: Once, spying a grass thief, he crept up and tapped the poacher’s backside with his weapon. The frightened man turned. Seeing Getaneh, his bladder failed. Getaneh laughs at the retelling. But his job also brings danger. Bandits—shifta—pass through, selling arms left behind from the civil war or from conflicts with Eritrea. Getaneh has been shot at and attacked with stones. One poacher with a knife tried to start a fight. Drunks in bars in nearby Mehal Meda have vowed to kill him.

These days theft usually means fines or jail. But memories here are long, and history is never far off. For centuries penalties were brutal, to serve as deterrents. Fines were to be paid in lion skins or cabbage seeds—neither found in Guassa. So authorities beat and excommunicated poachers. Illegally grazing cows were slaughtered, their skins stretched and given to the church for drums. Homes thatched with stolen grass were burned.

View Images Small farms hug the slopes of the Great Rift Valley and cover much of the Ethiopian Highlands, fragmenting geladas’ native grasslands. Many villagers around Guassa grew up trapping or beating nutrient-hungry monkeys that raided their crops. Most, today, simply chase geladas away.

We start hiking again. After a mile or so, Getaneh points out a fresh earthen pit. Around it, dirt is charred. Someone has cut and burned heather to make charcoal. We see small grass cuts. Poachers have been through. Getaneh heads to high ground and scans the plateau. “They are not here,” he says. I ask if he thinks he’ll catch them. He shrugs, sitting down. From his breast pocket he pulls a skull he’d found on the trail, probably from a duiker. It is no bigger than his palm. Without someone watching, he says, grass theft would be rampant. Farmers with sick cows would slip into closed meadows. As the grassland shrinks, monkeys would steal more from farms. That could lead to more dead monkeys.

We round a corner. Perched on a rock near a patch of Saint-John’s-wort, a brown francolin stares across the valley. Days earlier I’d walked near this spot with Kerby. He’d suddenly pulled up short, startled. A large spotted feline had rushed into the brush. This was not a serval, Kerby suspected, but a leopard. I think about that now, and about this place. Across Ethiopia a fraction of native highland vegetation remains. Yet Guassa is still ecologically rich. This ecosystem has survived revolutions, occupations, famine, and corruption. It has outlasted national governments. Under the right conditions, local conservation works. But ecosystems are fragile. The reign of the Derg, and subtle changes since, hint at how easily it can all come undone.

Guassa: A Sacred Place

Guassa farmers aren’t charmed by the monkeys. Villagers tolerate them. Smart geladas climb atop fresh-cut piles of barley to feast. Villagers chase off hungry monkeys raiding nutrient-rich row crops. When grass is well managed, there’s enough for people and monkeys. When the Derg was in power, some villagers say, grass was not managed well at all.

One morning Kerby and I picked our way through light rain down a steep, slick path to see Tasso Wudimagegn, a farmer and a scout for the Guassa Gelada Research Project. He had witnessed a transformation in Guassa. He had also undergone one himself.

Inside his mud-and-rock home, his wife boiled coffee over an open fire. We sat beneath walls papered with torn magazines displaying images from around the world—baseball games, smiling children, tranquil beaches. Growing up, he had despised geladas. He blamed the Derg, which had nationalized land and disbanded Guassa’s oversight, for inciting the hatred. Grazing and cutting increased. Many farmers believe grasslands shrank, and with more human encroachment on the monkeys’ natural feeding grounds, geladas raided farms more often. At the age of five or six, Wudimagegn tried scaring the monkeys off. Kids yelled and hit monkeys with stones. But geladas bared their teeth, and the children fled. When he grew older, he built traps. He beat geladas with an Ethiopian staff, called a dula.

These days Wudimagegn feels sheepish about such mistreatment. “I was wrong to think like that,” he said. Oversight in Guassa is better than ever, but the community is in flux. The property system has shifted. Once church based and limited to the descendants of its founders, Guassa’s stewardship is now more secular, more open to newcomers who don’t share its history. The underlying dynamic that makes local conservation work is the perception that everyone’s in it together. But now resentments are budding. A sense of belonging is eroding.

View Images As darkness falls on Guassa, geladas break into a run down a slope toward their sleeping cliffs. They will spend the night perched on narrow rocky ledges, trying to stay safe from leopards, hyenas, and feral dogs.

Wudimagegn admitted that he sometimes stares at his walls with longing. The magazines depict “better places,” he said. He wants to move to the city, make more money, give his children a better education. It’s a universal story—people want the life they see others have.

After an exhausting nine-hour walk, Getaneh, Kerby, and I reach Guassa’s end. We hitchhike toward Mehal Meda. Along the way a different landscape spills before us: acre after acre of rolling farms and crumbling earth, each plowed plot hugging the next in an unbroken sea of agriculture. That, Kerby says, is how most of the rest of the highlands look.

Guassa avoided that fate in part because locals kept control, rules were clear, oversight was strict, and users were invested. Nobel Prize winner Elinor Ostrom found that similar strategies also succeeded in places as disparate as Swiss farming villages, Japanese forests, and New England lobster fisheries. Comparable efforts are being employed in Namibia to protect wildlife. But Guassa for centuries was aided by elevation and remoteness, which kept newcomers at bay. Now new pressures are all around. The Derg is gone, but other parts of the country are again wrestling with political instability. Climate change is making higher land even more suitable for farming. By 2050 Ethiopia’s population could increase 10-fold from what it was in 1950, to 188 million. A country less than twice the size of Texas would have nearly seven times as many citizens. Incomes are rising, but one-third of Ethiopians still live in extreme poverty. So the government is encouraging Chinese investment.

View Images Two adult males look out over a landscape in transition. Agriculture is overtaking Ethiopia’s grasslands, and climate change is making higher ground more suitable for farming. With so many pressures, can protected areas like Guassa survive?

Making our way back toward Guassa, I see a meadow popular with geladas. Yellow tractors and earthmovers are paving a dirt road that skirts the meadow’s edge. Machinery is ripping up wetlands thick with nutritious vegetation. Power lines and cell towers and a rudimentary tourist lodge have all been built within the past decade. And why not? Life here is hard, opportunity is scarce. Development, ecotourism, and access to more markets could pull people out of poverty and help modernize the economy. But all this will put the region and its monkeys to the test.

Back in camp on one of my last evenings, Kerby and I follow the monkeys as they move in tight formation beneath a setting sun. One by one, amid their squeaks and grunts, the geladas clamber back over steep cliffs, where they will huddle until dawn on thin, rocky ledges. Honed over millennia, this practice protects sleeping geladas from hungry hyenas or other night-prowling predators. As I watch the stragglers break into a languid trot, it’s hard to escape a sense of unease. Evolution has prepared our fellow primates for many threats. But there will be no place to hide from what we’re about to throw their way.

Photographer and National Geographic Grantee Trevor Beck Frost finds joy in places “where nature is wild and as it should be.” Photographer Jeffrey Kerby, also a National Geographic grantee, is a scientist at Dartmouth. This is their first feature for the magazine.