Colours of Wildlife: Gelada

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Gelada

Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

Gelada by Willem


This week I bring you one of Africa's weirdest and least known critters, the Gelada, Theropithecus gelada. Its genus name means 'Beast Monkey' in Greek. It is indeed one of the most fearsome looking of all primates, but in reality is very gentle most of the time. Geladas are quite big, the male reaching 22 kg/50 lbs, the female 15 kg/33 lbs.

Grass-eating Monkeys of the High Plateaus


Geladas occur only in Ethiopia, and only in high parts of the mountains. Two subspecies are recognized, separated between the northern and southern ranges of the Ethiopian highlands. They specifically seek out areas of grassland on plateaus, called High Wurch or High Puna grassland steppe. They are unique amongst the primates for feeding primarily on grass, with only 10% of their diet consisting of other plants, fruits, and invertebrates.


Because these grasslands are situated so high in the mountains, up to 4400 m/over 14 000' above sea level, the climate can be very cold, even though Ethiopia lies within the tropics. This is why geladas have long, shaggy fur on their heads, necks and backs, especially long in the males, forming a large 'cape' that can cover the entire body and keep them warm. Geladas feed during the day and retreat to ledges amidst the high cliffs at night. Here they huddle together to keep warm. It is incredible how these monkeys confidently crowd together on extremely narrow ledges above dizzyingly perilous drops. But of course these positions, pretty much inaccessible to any predators, give them considerable safety provided they don't lose their footing and fall!


Grass is rather poor in nutrition, as a result of which Geladas are not very active. Most of their time consists of sitting down and nipping off grass leaves with their fingers. They will shuffle around on their backsides as they forage, without actually getting up. Since the high mountains receive lots of rain, grass is usually abundant, but sometimes there are droughts, or sometimes livestock will overgraze some of the gelada's feeding grounds, in which case there might be a grass shortage. In these cases, the geladas will dig into the ground to get at the subterranean stems and rhizomes of the grass. This can temporarily eradicate grass from the area, creating what is known locally as a 'gelada field'.

Butts and Bleeding Hearts

Gelada by Willem


One of the most distinctive features of the gelada, seen from the front, is the naked, roughly hourglass-shaped patch of pinkish-red skin on its chest. In the male, this is the brightest and most noticeable most of the time. In the female, this naked patch is a bit less conspicuous, except when she is in heat. Then, the naked skin becomes swollen, and outlined around the edges with round, blister-like pockets called vesicles. The reason for this bright red chest skin is linked to the gelada's feeding behaviour. In other baboons, the female's buttocks plays the role of signalling to males that she is ready to mate, in which case her buttocks become red and swollen. In the gelada, because these monkeys shuffle around on their butts most of the time, their buttocks are not plainly visible. Consequently the female gelada has had to evolve a different way of showing her readiness. Thus she has a patch of naked skin on her chest that mimics the naked butts of other baboons. So, she does not even have to get up to show the males that it's the right time for her. She also does get swollen naked skin around her butt, so on the rare occasion when she does get up, this too signals her sexual receptivity. Her butt has swollen vesicles all around the area of naked skin just like her chest … it is amazing how the two areas, anatomically having nothing to do with each other, look so much alike.


The question remains, though, why the male Gelada also has a naked patch on his chest that mimics the butts of the females. In his case, there are no swollen vesicles, and the naked skin remains bright red year-round. The genes that cause the red chest in the female, must also have an effect in the male. This naked patch probably also now functions as a general social signal in gelada troops. Geladas also have pink patches around their eyes, that can be accentuated by lifting their eyebrows or closing their eyes, that also are used as signals. Additionally geladas have lots of calls and chatter to each other as they graze.

Alien Faces

Gelada by Willem


Perhaps the weirdest and most fearsome characteristic of the gelada is its 'alien face' or lip-flip display. It is the only monkey that does this. Like baboons, geladas have extremely long and sharp canine teeth, especially in the males. In many baboons, grinning and yawning to show off the long teeth is used in display, to show dominance and to intimidate rivals. In the gelada, the yawn or grin is accentuated by a unique method. The upper lip can be flipped backwards and drawn back beyond the level of the nostrils, hiding the nose entirely and exposing a huge area of gums and making the teeth seem to protrude far forward. This is somewhat reminiscent to the creature in the 'Alien' films that thrusts its biting jaws forward from its mouth when attacking. It looks out-of-this-world, but actually the lip-flip grin is not always used in an aggressive way, instead being often used as a general greeting, as a smile so to speak.

A Glorious Past – but what about the Future?


The genus Theropithecus that the Gelada belong to, is related to the baboons and mandrills. In the not-too-distant past, monkeys of this genus thrived all over Africa and were even found in southern Europe and in Asia as far as India. Fossil relatives of the Gelada were also found here in South Africa, with bones turning up at sites quite close to where I live, at Makapansgat and Swartkrans. Some of the extinct Gelada relatives were huge, the size of the present-day Gorilla! We don't really know why they dwindled so much up till the present day. For some reason, the modern baboons of the genus Papio seem to have outcompeted them. It is not known whether the fossil Geladas were also so specialized in their dietary habits. They also had strong jaws and teeth and would have been good at eating grass, but perhaps had more diverse diets.


With the modern Gelada, at least, it is likely that its dietary specialization is the reason for its restricted occurrence. It probably evolved to this level of grazing specialisation because it could not compete with baboons as a generalist. But it also could not compete, as a grazer, with antelopes on the open savannahs. Consequently it finds its only niche in the Ethiopian highlands, the most extensive mountain system in tropical Africa. Here, because of the cliffs and steep slopes, there are no grazing antelopes that can easily reach the plateau pastures and meadows to compete with them. Domestic goats and some cattle now compete with them thanks to humans in at least some part of their range. Farmers are moving higher into the mountains as well, turning the meadows of the geladas into farmlands and shooting the geladas for raiding their crops. There are still around 200 000 geladas left, but their future depends on conservation. There have been proposals made for more nature reserves in the mountains, a move that would not only protect geladas, but also many others of the unique endemic animals and plants of the Ethiopian highlands.

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