The gelada (Theropithecus gelada), sometimes called the gelada baboon and bleeding-heart baboon, is a species of Old World monkey found only in the Ethiopian Highlands, with large populations in the Semien Mountains. Theropithecus is derived from the Greek root words for "beast-ape." Like its close relatives the baboons (genus Papio), it is largely terrestrial, spending much of its time foraging in grasslands.
Since 1979, it has been customary to place the gelada in its own genus (Theropithecus), though some genetic research suggests this monkey should be grouped with its papionine (baboon) kin; other researchers have classified the species even farther distant from Papio. While Theropithecus gelada is the only living species of its genus, separate, larger species are known from the fossil record: T. brumpti, T. darti and T. oswaldi, formerly classified under genus Simopithecus. Theropithecus, while restricted at present to Ethiopia, is also known from fossil specimens found in Africa and the Mediterranean into Asia, including South Africa, Malawi, the Democratic Republic of the Congo, Tanzania, Uganda, Kenya, Ethiopia, Algeria, Morocco, Spain, and India, more exactly at Mirzapur, Cueva Victoria, Pirro Nord, Ternifine, Hadar, Turkana, Makapansgat and Swartkrans.
The gelada is large and robust. It is covered with buff to dark brown, coarse hair and has a dark face with pale eyelids. Its arms and feet are nearly black. Its short tail ends in a tuft of hair. Adult males have a long, heavy cape of hair on their backs. The gelada has a hairless face with a short muzzle that is closer to a chimpanzee's than a baboon's. It can also be physically distinguished from a baboon by the bright patch of skin on its chest. This patch is hourglass-shaped. On males it is bright red and surrounded by white hair; on females it is far less pronounced. However, when in estrus, the female's patch will brighten, and a "necklace" of fluid-filled blisters forms on the patch. This is thought to be analogous to the swollen buttocks common to most baboons experiencing estrus. In addition, females have knobs of skin around their patches. Geladas also have well developed ischial callosities. There is sexual dimorphism in this species: males average 18.5 kg (40.8 lb) while females are smaller, averaging 11 kg (24.3 lb). The head and body length of this species is 50–75 cm (19.7–29.5 in) for both sexes. Tail length is 30–50 cm (11.8–19.7 in).
The gelada has several adaptations for its terrestrial and graminivorous (grass-eating) lifestyle. It has small, sturdy fingers adapted for pulling grass and narrow, small incisors adapted for chewing it. The gelada has a unique gait, known as the shuffle gait, that it uses when feeding. It squats bipedally and moves by sliding its feet without changing its posture. Because of this gait, the gelada's rump is hidden beneath and so unavailable for display; its bright red chest patch is visible, though.