Gelada, Theropithecus gelada
Geographic Distribution and Habitat
Geladas are only found in the grasslands of the Semien Mountains in Ethiopia. Their territories are lined with rocky cliffs, where they sleep at night, and are mostly filled with grassy meadows, with the occasional bush or tree marking the environment. The species is divided into two gelada subspecies—the northern and southern gelada, respectively—although there are so few differences between the two groups (i.e., the northern gelada have a bigger, rounder skull) that some researchers question if they should be classified as two separate subspecies.
Temperatures can vary greatly in these mountains, but monthly averages usually fall between 50°F (10°C) and 69.8°F (21°C).
Size, Weight, and Lifespan
Male geladas are far bigger than their female counterparts. Males can weigh up to 44 lbs (20 kg) and stand 29 in (74 cm) tall, while females weigh around 30.8 lbs (14 kg) and stand 24 in (60 cm) tall.
Geladas can live to be about 15 years old in the wild, and up to 28 years in captivity.
Living in close association in a way that allows one species to benefit without harming the other.
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Geladas are best recognized by a red, hourglass-shaped patch of skin on their chest that lends the gelada its nickname: “the bleeding-heart monkey.” For females, this patch grows more vibrant and blisters when they enter estrus.
Although closely related, geladas are not members of the baboon genus, but instead have their own genus, Theropithecus (Greek for “giant beast” and “ape”). Still, they have many characteristics similar to baboons, which is why scientists considered them to be true baboons up until 1979.
Geladas have a bare, brown face with pink eyebrows, which they display during threats. They have a pronounced snout that is noticeably shorter than a baboon’s snout. The northern gelada’s snout is slightly longer than the southern gelada’s snout. Males in particular have long brown and golden hair on their heads, shoulders, and backs, making them look bigger.
Geladas are adapted to a life of grazing. Their fingers are short and stubby to pick out grass and seeds. Although they have the same menacing canines as their baboon cousins, the rest of their teeth are designed for grinding up plants, with their jaws moving side-to-side like a deer or a cow. Their backsides have extra padding to allow them to sit down for long hours while they shuffle around in search of food. Because geladas spend most of the day sitting, there is no need for them to have a brightly-colored backside like baboons; this is likely the reason why they developed such flashy chests.
90% of the gelada diet is made up of grass (blades and seeds alike), making them the only primates with a majority grass diet. They will also eat roots and flowers when available. However, they are not complete herbivores, as they will eat insects on rare occasions, though it is never a priority meal.
Because grass is lacking in nutrients, geladas must spend 10 hours a day foraging, compared to just 4 hours a day for the average monkey.
Behavior and Lifestyle
Being diurnal animals, geladas sleep at night and are most active during the day. They awake at sunrise on the cliffsides, where they can be safe from predators during the night. They only climb trees when performing sentry duty or escaping predators (although they will usually scale the nearby cliffs to escape predators).
In multiple cases, geladas seem to have developed a commensal relationship with Ethiopian wolves. Although geladas are fearful towards all other canines, the wolves walk freely among gelada families while searching for smaller prey. Wolves are twice as successful when hunting for rodents among geladas, but the geladas do not seem to benefit from this relationship, as the wolves are too small to protect geladas from their major predators.
Geladas live in a complicated society defined by both violence and diplomacy on multiple levels. They live in reproductive units consisting of 2–12 members, headed by a dominant male. Usually the unit will consist of the dominant male and female, a few related females with their offspring, and sometimes a few other males. Several reproductive units will join together to form a band, which can have well over a hundred members. Occasionally, bands will join up into herds of several hundred members for short periods of time.
A dominant male comes into power either through battle with the previous ruler or by intimidating him into submission. However, if a male gelada intends to keep his power, he must win the support of the dominant female and her relatives. Just like a king needs to convince his nobles that he’ll serve them well, a dominant male gelada must continually prove to the dominant females that he can sire the best offspring, protect his band from predators and rogue males, and dedicate enough time to grooming his mating partners.
The dominant female also gets to decide who the dominant male can mate with. In some cases, the male may mate with several females, while in other cases the dominant female will demand exclusive mating rights.
Because geladas spend so much time foraging, they are unable to properly bond through grooming, like many other primates. To make up for this, geladas verbally communicate far more than most other primates. Walk through a band of geladas foraging and you will be deafened by the sounds of grunts, groans, and squeals, over 30 of which have been identified by researchers so far. They have been known to string together these noises in rapid succession and use their lips to manipulate the sounds to produce calls that many people would find surprisingly human.
The chest of a female gelada will become red and blistered when she is ready to mate. The mother will be pregnant for just under 6 months. She’ll then carry her newborn around for 5 weeks until the baby is strong enough to cling to the mother’s back, where the baby will spend most of his time for the next 5 months.
Females stay with their families for their entire life, usually reaching maturity around 4 years old. Males, on the other hand, begin to separate from their families when they hit puberty at 4 or 5 years old. They will generally spend the next few years with a small group of males waiting for an opportunity to take over a reproductive unit of their own.
As grazers, geladas play an important role in their ecosystem. Feeding on grass prevents the accumulation of dead grasses, which can provide fuel for wildfires.
Animals that may prey on geladas include wild dogs, leopards, and a few birds of prey.
The International Union for Conservation of Nature gives the gelada the status of Least Concern (IUCN, 2018), writing: “This species has a large range and is still abundant despite increasing threats to the species and is hence listed as Least Concern. There is no reason to believe it has undergone a significant range-wide decline that would warrant listing in a threatened category.”
Ethiopia is currently the fifth fastest growing economy in the world and is one of the faster growing populations. Due to this, there has also been a rapid expansion of agriculture into gelada territory. Goats and cows compete with geladas for patches of grass, leading farmers to either shoot geladas or force them into lower quality grasslands.
With the entire gelada wild population endemic to Ethiopia, it also important to look at the government’s environmental policies as well as overall stability. The IUCN states (above) that there is no reason to believe the gelada population has significantly declined, however, it should be noted that Ethiopia underwent a brutal civil war from 1974 to 1991, leaving a massive gap of time when researchers could not safely work in the country. During this period, the gelada population may have dropped by half, but there is not enough research to confirm that.
Since the war, Ethiopia has stabilized, but there is currently rising tension between the authoritarian government and opposition groups. Conservation groups prefer to work with stable governments to ensure that their money will be well spent. These groups will be watching Ethiopia closely over the next few years.
The largest populations of geladas live on protected lands where hunting is forbidden, and more protected areas are currently being considered. The gelada benefits from sharing habitats with endangered species such as the Ethiopian wolf and the mountain nyala. Even on unprotected lands, killing or trapping geladas is outlawed unless permitted by the government in the name of science or national interest.
In partnerships with local governments and other charities, the African Wildlife Foundation is looking to support tourism in the Semien Mountains, giving local towns a financial incentive to protect native wildlife.
- “Speech-like vocalized lip-smacking in geladas.” By Thore Bergman. Current Biology, Vol. 23 No. 7, 8 April 2013.
- Monkey Planet (2014) http://www.bbc.co.uk/programmes/p01r52gr
- Baboon King (2017) https://www.smithsonianchannel.com/shows/baboon-king/0/3437510
Written by Eric Starr, March 2018