The average body mass for an adult male gelada baboon is around 20 kilograms, and for the female it is between 13 and 16 kilograms. The males have a large mantle or mane surrounding their head. On the chest of both sexes are hairless patches of skin that are heart shaped in males and hourglass shaped in females. Surrounding this skin are bumps of skin that swell up for the female during estrus. This area on the chest mimics the sexual skin during estrus probably because since the gelada baboon sits for long periods while it forages for food, the male would have a difficult time seeing the perineum. At the tip of the tail there is a tuft of hair.
The gelada baboon is found in the country of Ethiopia. This species lives in montane habitats including scrubland, grassland, and some types of woodland. The gelada baboon does not live in elevation above 4500 meters. Because this species sleeps on outcroppings of rocks, it needs rocky areas in its habitat.
The main food consumed by the gelada baboon is grasses with the blades, seeds, and bulbs especially being eaten. This species will also eat fruit, insects, flowers, and leaves. The gelada baboon will forage sitting down and shuffle along the ground, and they pick up grass blades using the thumb and index finger (Richard, 1985). This is a diurnal species. The gelada baboon sleeps on outcroppings of rock at night.
The gelada baboon moves on the ground quadrupedally (Fleagle, 1988).
The basic unit of the gelada baboon social structure is the unimale group which consists of one male and several females. Next tier of the gelada baboon social system is the band which is a cluster of associated unimale groups (Kawai et al., 1983). The next level is the herd, which is a temporary aggregation of bands that come together usually during the dry season for grazing (Stammbach, 1987). Unimale groups can switch between bands, unlike the Papio hamadryas bands which are more stable (Stammbach, 1987). Males that are not part of unimale groups form all male groups which forage on their own and sleep separately from the unimale groups (Stammbach, 1987). A male can become a leader of a unimale group by capturing females and starting his own unimale group or by gaining up on a weak leader of a unimale group with help from other members of a all male group (Stammbach, 1987). Males can also be).
social presenting: This is like presenting, but is done by females and juvenile males towards higher ranking males (Estes, 1991). This is a submissive display and differs from presenting by the hindquarters being lower.
staring: This display by the gelada baboon is used as a threat display (Estes, 1991). The eyes are fixed on the stimulus and the eyebrows are raised and the scalp is retracted, the facial skin is also stretched by moving the ears back (Estes, 1991). Underneath the eye lids the color is different which contrasts sharply with the surrounding facial color (Estes, 1991)
staring with open mouth: This is the stare accompanied by the mouth being open but the teeth are covered (Estes, 1991). This is a threat expression and often occurs with head-bobbing (Estes, 1991).
head-bobbing: This is used as a threat display by the gelada baboon and head bobs up and down (Estes, 1991). This often occurs with staring with open mouth (Estes, 1991).
social grooming: This is when one individual removes parasites and dead skin with their hands from another individual. In this species it generally only occurs between same sex individuals. This is used to reinforce the social bonds.
nose-to-nose greeting: When two individuals meet each other they touch noses as a friendly sign (Estes, 1991).
social mounting: This is generally a response to social presenting and serves to signal a friendly reassurance (Estes, 1991). This is also seen during aggressive encounters (Estes, 1991).
The hamadryas baboon gives birth to a single offspring. During estrus the perineum of the female swells up.