Splendor in the Grass

December 2007

Chewbacca is one of 300 gelada monkeys I have been studying in Ethiopia for the past ten years. He is an impressive beast with a billowing mane that shimmers in hues of gold and chocolate. His tail is lion-like with a golden tuft at the end, his shoulders broad and powerful. On his chest is an hour-glass-shaped patch of bare pink skin.

If Chewbacca is in an aggressive mood, he’ll stare me down with a piercing amber gaze. Direct eye contact is a threatening gesture in gelada society, and I usually give in, dropping my eyes to my clipboard and muttering some apologies. It’s not easy conducting observational research out of the corner of your eye, but if I continue to stare Chewbacca will react by pulling his upper lip over his nose and flashing pink gums and glistening canines at me. Generally I watch my gelada manners when I’m sitting beside him.

But it wasn’t always like this. When I first came to the Simien Mountains National Park in northern Ethiopia to begin a Ph.D. on the behavioral ecology of the gelada, I wasn’t able to get anywhere near them. My supervisor, Professor Robin Dunbar, had been the last person to study geladas in the early 1970s, but since then Ethiopia had languished in a dark 20-year period of bloody civil war. The remote mountain home of the gelada saw some of the worst fighting, and no foreign scientist had been able to return since. It seemed like a golden opportunity to me, and at the ripe age of 25 I stumbled into Ethiopia with naïve dreams of learning local dialects to track down the last remaining gelada. Instead I was handed an AK-47 and told where to watch out for landmines. It was no surprise gelada were keeping a low profile.

Geladas now call the alpine highlands home

Although commonly called baboons, geladas differ from their better known Papio baboon cousins by occupying a genus all of their own, Theropithecus gelada. Three million years ago the Theropithecines were a highly successful genus of grass-grazing primates—many of them the size of gorillas—roaming throughout Africa and into Europe and Asia. As the African continent dried out and the grassland shrank, only the runt of the genus survived. The gelada is now considered a relict species, eking out a living as the world’s last grass-eating primate in the last fragments of high altitude Ethiopian grassland.

The gelada’s habitat is a spectacular mix of canyons, spires, and escarpments. At my field site in the Simien Mountains you can admire views reminiscent of the Grand Canyon or Hawaii’s volcanic ridges or the Alaskan tundra just by turning 360° on one spot. Add to this the sight of hundreds of monkeys grazing on an alpine plateau at 13,000 feet and you have a truly breathtaking spectacle.

After a long day of shuffling along on their backsides and shoving their faces full of grass, the gelada tumble over sheer cliffs and sleep on narrow ledges to avoid the nocturnal threat of leopards and hyenas. As I retire to my sleeping bag and tent to avoid howling winds, lashing hail, and sub-zero temperatures, my thoughts are with Chewbacca and his family clinging to their sheer rock face in the dark.

Most dawns are spent sitting at the top of the sleeping cliffs waiting for the geladas to clamber up and join me on the plateau. I have a thermos of Ethiopian coffee—the best in the world—binoculars, and a notepad with hundreds of gelada faces sketched for identification. On each one I have tried to mark the tiniest of scratches and imperfections, their faces being frustratingly uniform. The gelada’s day always begins with grooming, the social glue that holds their society together. It’s a peaceful time of day and the best opportunity I have for studying their complex social relationships.

800 unique monkeys

Deciphering patterns of relationships within a herd of monkeys that sometimes numbers 800 individuals was daunting at first, but we now understand that geladas have one of the most complex social systems of any primate. Called ahierarchical system , if we analyze it closely the herd of 800 can be broken down into ever-smaller units of association: from herds to bands to tribes to units, down to pairs of gelada that might form life time grooming dyads. But the basic building block of gelada society is the Family Unit, made up of around three to eight related females and their offspring. Each Family Unit has a dominant alpha female and a distinct internal hierarchy. These related sisters, mothers, and daughters choose a single unrelated adult male to be the family “patriarch.” In deciding on a male, the genes shared by females within each family provide a powerful bond for consensus, and the new male, despite being twice their size, learns quickly not to mess with the sisterhood. But choosing the male is not always a smooth affair, and the females’ “democracy” is often beset by fierce internal fights. If the family is large like Chewbacca’s, it becomes increasingly difficult to keep all the females happy. They have their sexual cycles together, and there’s only so much Chewbacca to go around. Cracks may begin to appear in the social network of the family, and this may lead to a splinter cell of females, often a mother and daughter, breaking away and forming a brand new unit. Chewbacca might be impressive to look at, but females call the shots in gelada society.

Geladas always look for where the grass is greener

The gelada’s dependence on a grass diet has led to a number of other unique traits. Without the ability to digest cellulose, geladas must rely on plucking and eating vast quantities of carefully chosen young green grass blades. This has endowed them with the highest “opposability index” (the ability to touch thumb to fingertips) of any nonhuman primate, making their hands incredibly dextrous. In order to graze more efficiently, gelada shuffle along on their haunches keeping both hands free to pluck grass continually. Unfortunately, this leaves a primate’s most common sexual “signpost,” its rear, invisible for large parts of the day. Natural selection has overcome this problem by shifting the gelada’s sexual display to the chest, where both males and females have a bare hourglass-shaped patch of skin that varies in shades of pink depending on their hormonal state.

The future of a relict species?

As a behavioral ecologist I was entranced by the gelada’s extreme ecological adaptations and rich social life. But it took some years for my eyes to open to the broader issues of conservation in the Ethiopian highlands. After the civil war came peace—and a new wave of human population into the mountains: subsistence farmers with few alternatives but to plough up alpine grassland and plant barley. An uneasy truce existed while geladas learned to graze alongside domestic goats and cattle. As long as the geladas stuck to grass it seemed they might be a rare example of an African primate living in relative harmony with its human neighbors. The gelada’s other saving grace was a devout Orthodox Christian peasantry who would prefer to starve than turn to bushmeat. If geladas had lived in certain other African countries, their docile nature and open habitat would have led them to extinction long ago.

We currently estimate the total gelada population to be in the region of 100,000 to 200,000. These numbers sound reasonably healthy, but mountain wildlife suffers from the “island effect,” in which subpopulations are isolated from each other and are highly sensitive to small ecological perturbations. Gelada socio-ecology has been shown to be remarkably sensitive to average ambient temperature. There is no doubt that a small increase in average global temperatures would push the gelada’s protein-rich grasses higher in altitude. This can already be shown by comparing images from Prof. Dunbar’s study with mine 30 years later. What is less certain is how great an increase in global temperatures would be needed to drive the grasses, and thus geladas, off the top of the mountains entirely. Geladas are approaching the altitudinal limits of their habitat, and I often describe them as sitting on their mountain roof-tops watching the proverbial flood waters rising around them.

The theoretical effect of climate change on geladas is largely a matter for speculation. A more immediate concern is with the gelada’s own public relations in Ethiopia. As the Ethiopian highlands become increasingly crowded, farmers are complaining more vociferously that ever more geladas are raiding their barley crops. Very few Ethiopians know that geladas are an endemic species and an animal, like the rare Ethiopian wolf, that they can be proud of and invest in. Despite boasting the greatest number of endemic species of any mainland African country, Ethiopia has not had the chance to develop an ecotourism industry like its neighbor to the south, Kenya. As the years of war and famine gradually fade into Ethiopia’s history, our hope is that more visitors will be attracted to the stunning natural scenery of the Ethiopian highlands and charismatic wildlife that can be found nowhere else on earth. A unique monkey that had been forgotten so long now needs as much attention as it can get.