London: My interview with the fab gelada researcher Aliza le Roux, who I met in the Simien Highlands of Ethiopia, is being broadcast in a Discovery programme for BBC World Service. So I thought I’d show you how magnificent these endangered, chatty primates are in a slide show of Nick’s pictures. You can watch the slide show while you listen to the programme. (For some reason, I can’t display image descriptions in the slideshow, so I’ve put caption information below the slideshow.)
Unique monkey: With an extraordinary mane of luscious hair, a bright-red, hourglass-shaped patch of bare skin on its chest and a chimp-like muzzle, the gelada baboon (Theropithecus gelada) is a highly distinctive – and very chatty – primate. It is the most ground-dwelling of primates after humans and, like us, has a fat-cushioned backside for more comfortable sitting.
Not true baboons: Geladas are not true baboons but the last surviving species of the theropithecus genus of terrestrial, Old World monkeys that once ranged throughout Africa and from Europe to Asia. It is estimated that just 50,000 geladas remain of a population that has shrunk by 75% over the past decade.
High plateaux: Geladas are now limited to the high plateaux of northern Ethiopia, most commonly in the Simien Mountain range, north of the town of Gondar. This range, with peaks above 4,500 metres, was formed from build up of volcanic basalt layers, which the wind and rain have eroded over time to leave steep escarpments, valleys and deep crevices. Four important African rivers, including the Nile, originate in these mountains, which are geologically similar only to the Drakensberg range of South Africa.
Life on the edge: The steep precipices offer excellent refuge for geladas and they sleep on the cliff-faces at night, safe from leopards and other predators. “An alarm call from one of the group will alert the rest to the threat and the entire population will flee over the cliff’s edge in seconds,” says Aliza La Roux, a gelada researcher from the University of Michigan.
Human threat: The main threats geladas face are from the spread of human habitation. Ethiopia’s population already tops 80 million and growing at a rate of 2.6%.
Competition for grazing: It means that people are moving to new areas including in the Simien Mountains, planting crops in places where gelada food once grew, and bringing their dogs with them. “Geladas are terrified of dogs. So many have been killed by them,” La Roux says.
Competition for grass: Grazing by cattle and sheep is also impacting the geladas. Villagers are not allowed to graze their animals inside the Simien Mountains National Park’s protected areas, but rangers seldom act to stop them. As much as one-fifth of the Ethiopian population relies on food handouts to survive, putting enormous pressure on what little grazing there is.
Warming slopes: Geladas’ diet consists almost entirely of high-alpine grass, which is rich in protein. The monkeys spend a large part of each day sitting on the ground, plucking and eating this grass. Over the past decade, warmer temperatures and infrequent precipitation have reduced the amount of grass available and affected the plant’s protein levels, making it less nutritious.
Large groups: In common with other primates, geladas live in harems consisting of a dominant male, several females and youngsters. Deposed or elderly males are sometimes allowed to remain in the harem. Groups often band together in large populations of hundreds of individuals.
Tree climbers: Geladas spend most of their time on the ground, but they do climb trees and younger members of the group use the extra height to jump on their unsuspecting siblings during play.
Suckling mother: Female geladas have red, fluid-filled ‘beads’ on their chests, which exude an olfactory signal during estrus. They suckle their young for the first 6 months, after which ‘carer males’ in the group may assist in looking after the infant. Only the alpha-male gets to mate with the females.
Young geladas: Infants spend much of their time playing under the protective care of the whole group. Adult males who are threatened by a female or the alpha male will often grab an infant gelada, safe in the knowledge that no member of the group will attack a gelada that is carrying a baby.
Bachelors: When a male reaches maturity, at about 3-years-old, he is kicked out of the harem and finds his place in a bachelor group of similarly fated geladas, who follow the main band, waiting for an opportunity to enter a harem.
Bleeding heart baboons: Geladas are known as ‘bleeding heart baboons’ because of their livid chest markings, which change colour according to their arousal and may be used for signalling in a similar way to the red-coloured buttocks of true baboons.
Lion monkeys: The long mane and tail tuft of the male geladas has led them to be also called the ‘lion monkey’.
Teeth and all: Males are bigger than females and have longer canines that they display during ferocious-looking lip-flicking displays of aggression. Most fights consist mainly of posturing and it is very rare for a gelada to kill during a fight.
Listening in: Geladas have more vocalizations than any other primate and spent a large proportion of time sitting in the grass chatting. La Roux is recording their conversations and trying to understand more about geladas’ complex social hierarchies using various playback methods. She is the first scientist in 30 years to study the monkeys after years of war and civil unrest put the region off-limits to researchers. “They are wonderful research subjects, because unlike other primates, they don’t hide away in the tree tops, and they talk constantly,” she says.
David, an ex-pet: During my visit, La Roux and her assistant are given delivery of a young male gelada called David, which has been kept as an illegal pet.
Nervous youngster: La Roux introduces David to the group she studies, hoping to release him. But David is nervous and climbs her head for safety. It takes 4 separate attempts but eventually, he integrates successfully into the group.
Wandering Gaia 
Fabulous!