These monkeys are not actually true baboons, as their nostrils are located further from the end of their muzzle, but they resemble baboons in appearance.
The gelada baboon is the only species of grazing monkey. It is not closely related to other types of baboon. It is so named because it shares the characteristic of living on the ground with true baboons. The gelada baboon’s ancestors used to range over a much wider area. It is the last survivor of a group that once extended as far as India.
Geladas live in a very specific habitat: the grasslands found high up in the highlands of Ethiopia and Eritrea. The monkeys live in large groups, which are often based near rocky gorges where members can find sleeping sites on the cliffs that are relatively safe from predators. Each troop is broken down into harems, which contain a single dominant male and several females. The members of a harem frequently groom each other to maintain a strong social bond. These family groups may sometimes gather into large troops of several hundred animals. Young and unattached males may form their own social units.
Geladas have long side whiskers, a mane of hairs on the neck and three bare red patches of skin on the chest and throat, which the male expands and brings into full view in his aggressive, threat posture. Males have facial hair and a cloak-like mantle of hair. Females are about half the size of males and have much lighter manes.
In the morning, the geladas leave the cliffs where they have slept and move off to alpine meadows, where they feed largely on plant material, such as grasses, seeds and fruit. They do not have a specific territory, and the male keeps his family together by means of a variety of calls and facial gestures. Geladas have excellent vision.
Geladas have the most dexterous hands of any African monkey. They are used to pluck just the juiciest grass stems and dig up roots. Geladas have been known to raid cereal crops, which are a manmade grassland. Despite being protected, geladas are often killed by farmers. The red patch on the chest, which becomes more swollen in females when they are in oestrus, is similar to the skin in the genital region of baboons. It has evolved on the chest, however, because geladas spend most of their time sitting on their buttocks.
Most young are born between February and April. The female produces a single offspring, rarely twins, after a gestation period of between 147 and 192 days. The mother suckles the young gelada for up to 2 years and after giving birth, she will not have a period of heat for another 12 to 18 months.
Distribution: Restricted to the highlands of northern Africa, occurring at altitudes of 1400 - 4400 m (4600 - 14,400 ft) in open areas of grassland in Ethiopia.
Habitat: Highland meadows.
Weight: 11 - 20 kg (24 - 44 lb); males about twice as heavy as females.
Length: 82 - 114 cm (32 - 45 in).
Maturity: Females around 4 - 5 years; males 5 - 7 years.
Gestation Period: 150 - 180 days.
Breeding: 1; weaning occurs at 12 - 18 months.
Diet: Herbivorous, having adapted to feed on grass, although eats roots in the dry season.
Lifespan: Up to 30 years.
Smaller than males, females also lack the longer mane of fur.
The hair at the tip of the female’s tail is much longer than in males, forming a tuft.
The bright red patch of skin on the chest is another way of distinguishing this species from baboons.
The thumb is very flexible, helping these monkeys to pick shoots of grass easily.
The head profile differs between sexes, with the nose of the male (bottom) quite different to that of the female.
Geladas live in harems comprising a male with several females, which come together in areas where food is plentiful.
Male and female gelada baboons have a very different physique and appearance once they reach maturity.