The gelada, also famous as gelada baboon, is a species of monkeys that belong to the primate family Cercopithecidae (Old World Monkey). Although the geladas are closely related to baboons (genus Papio), they are not true baboons because they belong to the genus Theropithecus. They derive their nickname, the ‘bleeding-heart monkey’, from the brightly colored patch of skin that is shaped like an hourglass on its chest. The geladas are classified into two subspecies, including the northern gelada and southern or eastern gelada. They are, at present, found only in Ethiopia.
Size: Males are larger than females. The combined length of their head and body ranges between 19.7 in and 29.5 in (50 cm and 75 cm) for both sexes. They have a tail that can measure anywhere between 11.8 in and 19.7 in (30 cm and 50 cm).
Weight: The males have an average weight of 40.8 lb (18.5 kg), while the females being smaller weigh less with an average weight of 24.3 lb (11 kg).
Color: Their body is covered with dark brown or buff hair, while their face is dark with pale eyelids. They have black arms and feet, and a bright red, hourglass-shaped skin patch on their chest.
Body: They have a large, robust body with a heavily furred back. Their face is hairless, while the short muzzle is similar to that of a chimpanzee. Geladas have a short tail with a tuft of hair in the end. They also possess a well-developed callosity, which is the skin on the back of their hip bone that becomes thickened due to repeated friction or contact.
Sexual dimorphism: On males, the hourglass-shaped skin is bright red outlined by white hair. The females, on the other hand, have a less conspicuous patch of skin. Females in estrus, however, have a bright patch with a ‘necklace’ of blisters on it.
The Geladas are distributed in the mountainous regions of the central Ethiopian plateau. Most of the gelada monkeys live in the Sankaber and Gich regions of the Simien Mountains in Ethiopia.
What Kind of Habitats do Geladas live in
They are found at elevations of 1,800-4,400 m above the sea level. They use the rocky cliffs for sleeping at night and montane grasslands with dense thickets, bushes, and widely spaced trees for foraging.
While geladas may live for about 14-20 years in the wild, they have a longer average lifespan in captivity. A captive gelada has been recorded to have lived for about 30 years.
About 90 percent of their diet comprises of grass (both the blades and seeds). When both the seeds and blades are accessible, they prefer eating the seeds. They will also eat flowers, roots, and rhizomes when available. They are, however, not completely herbivorous primates because they occasionally eat insects that are easily obtained. Geladas chew their food just like zebras, which means their feeding behavior is quite similar to that of ungulates.
Geladas, being diurnal animals, sleep on the ridges of cliffs at night. They leave these cliffs at sunrise and then travel to the highest parts of the plateau to graze and socialize.
Their social activities decrease, and they mainly focus on searching for food after the morning ends.
They live in a complicated multilevel society. The smallest groups consist of reproductive units, which comprise 2-12 females, their offspring, and about 1-4 males, as well as the all-male units that consist of 2-15 males. About 2-27 reproductive units, along with several all-male units, form a band. Communities contain about 1-4 bands with overlapping home ranges.
The females form strong social bonds within their reproductive units, and each of them usually interacts with a maximum of three other members of the unit. Social interactions like grooming typically occur between pairs.
Females are aggressive towards members of other reproductive units. Males from both sides may join and fight if the clash becomes violent.
All-male units are also aggressive towards other all-male groups and reproductive units.
Adult gelada monkeys produce different vocalizations for different purposes, which include aggression, defense, contradiction, solicitation, fulfillment, contact, and reassurance. They sit idly and chatter at other members of the group.
The geladas display aggression or threat by the ‘lip flip’, an act of eversion, by which they turn their upper lips inside out on their nostrils to demonstrate their gums and teeth. They also pull their scalps back to reveal their pale eyelids.
Geladas have small, sturdy fingers, which help them in pulling grass, roots, and tubers. Their small, narrow incisors are adapted for chewing grasses, flowers, and roots.
Their unique gait, called the ‘shuffle gait’, facilitates them in eating grass. They move into position by squatting bipedally and then sliding their feet. This movement does not require them to change their posture.
Mating and Reproduction
Although breeding and reproduction occurs throughout the year, some areas have a peak season when the birth rate increases. It has been found that the birth rate becomes higher in the rainy season. When a female gelada is in estrus, it points her back towards a male in the group and moves its tail aside. The male approaches and looks closely at the female’s chest and genitals. Female geladas may copulate up to 5 times a day, typically around midday.
After a gestation of 5-6 months, gelada monkeys give birth to an offspring. The births usually occur at night, one baby at a time. Newborn babies weigh about 464 g, and they have red faces with closed eyes, while their bodies are covered in dark hair. Lactation lasts for 12-18 months, with the males attaining sexual maturity at 5-7 years of age and females becoming sexually mature at 4-5 years of age.
As of 2008, the gelada population has decreased to approximately 200,000. Still, the IUCN Red List has registered it as ‘Least Concern’ in 2008. Major threats to their population include the expansion of agricultural land, killing as crop pests, using them as laboratory animals, and hunting them for obtaining their capes. Conservation efforts have been initiated to protect the gelada population in Simien Mountain National Park.
The bleeding-heart monkeys spend most of the time sitting down, pulling out grasses and herbs, and eating them.
Geladas are the only extant species of primates that feed primarily on grass.
An alliance has been observed between geladas and solitary Ethiopian wolves. In most of the encounters, the monkeys would not move even when the wolves were right in the middle of their herd.