Theropithecus gelada
gelada baboon

Gelada baboons are found only in the highlands of Ethiopia and Eritrea. A majority of gelada baboon populations live in Gich and Sankaber areas of the Semien Mountains National Park in Ethiopia.

Gelada baboons are found inhabiting the high grasslands of Ethiopia and Eritrea, especially in the Semien Mountains National Park. Geladas prefer to sleep on rocky cliffs, from which they descend in the morning to go foraging in the nearby grasslands. Most of the gelada populations are found foraging in grasslands between 2,000 and 5,000 meters (Stammbach, 1987). This is a terrestrial species and is very specialized to this particular habitat. (Stammbach, 1987)

Male gelada baboons weigh an average of 20.25 kg. Their bodies are 69 to 74 cm in lenth while their tails are an extra 45 to 50 cm long. Female geladas are somewhat smaller. They weigh an average of 14.8 kg, are 50 to 65 cm in body length and their tails are 30 to 41 cm long. (van Hooff, 1990: 258)

Members of both sexes have short rostrums and wide nostrils. They have short brown fur and both males and females have a hairless patch on their chests, usually triangular in shape, which is outlined by white hairs. The color and size of this patch in both sexes is dependent on hormonal changes in the females. Both sexes have pale eyelids which are used for expression. Males are marked by the presence of whiskers and a brown hairy mantle. (Stammbach, 1987; van Hooff, 1990) (Stammbach, 1987; van Hooff, 1990)

Copulation is usually initiated by the female and occurs between the estrus females of a group and the group's male leader (Stammbach, 1987; Smuts, 1987).

Gelada baboons do not have a specific mating season, though it has been noted that the birth rate is higher during the rainy season. When a gelada female comes into estrus a ring of red beading develops in the naked patch on her chest and her ano-genital region swells visibly. The estrus cycles of females within a group are fairly synchronized, as are births. This may be due to social influence (Kawai, 1979).

Gestation length in gelada baboons is estimated at 5 to 6 months. Females generally give birth to one infant at a time and females with infants are anestrus (Smuts, 1987; Kawai, 1979). Lactation lasts for about 12 to 18 months. Females reach sexual maturity at about 4 or 5 years of age, but males do not become sexually mature until 5 or 7 years.

As in other primates, parental care is primarily the responsibility of females. Females must carry, groom, nurse and protect their offpspring until the young are independent. The role of males in the care of offspring is not well understood.

A captive gelada is reported to have lived well over 30 years. Lifespan of these animals in the wild has not been reported, but is presumably less than that seen in captivity.

Gelada baboons live in groups of one male with several females and their offspring. These groups are called one male units, or OMUs. Associated OMUs may travel in the same area making up a second level of organization called the band. OMUs have been known to travel amidst several different bands at different times or even alone, so membership within a band is not permanent. Geladas are not territorial and it is not uncommon to find congregations of separate bands grazing together wherever conditions are favorable. Outside of these social organizations are groups consisting entirely of males, or AMUs (Stammbach, 1987).

Grooming is exhibited by all members of an OMU. Grooming between the females and their male and is very important to the social stability of the group. When OMUs grow beyond capacity, the male is unable to give grooming attention to all the females. When this happens, unity within the group is lost, leaving numbers of females unattended and able to form new groups with males from roaming AMUs (Dunbar, 1987).

The females within an OMU are generally the true leaders of the group. If an outside male attempts to take over the group by supplanting the male using physical force, the females may choose to support or oppose either male. Regardless of who wins the fight between the two males, the females can chase the unwanted male from the group with their own show of physical force. Since only the male associated with the OMU is in a position to mate, the females have indirect control over male reproductive success (Smuts, 1987).

Primates typically have complex social communication involving visual, tactical and accoustic symbols. Sometimes, chemical cues are also used.

Geladas use visual signals, such as facial expression and body posture, to communicate with one another. There are also visual signals associated with estrus, such as the reddening of the chest patch in females.

Geladas make a number of vocalizations.

In addition, tactile communication, between mates, between grooming partners, as well as between mothers and their young, can be important in maintaining social bonds.

Some chemical communication is apparently also present in this species, as males often smell the reddedned chest patch of estrus females.

Gelada baboons are exclusively herbivorous, but their choice of food changes depending on seasonal availability. During the wet season (July and August), when green grass blades are abundant, they make up 93% of the diet of these baboons. In November, when the grasses have seeded, the seeds make up 70% of their diet. During the dry season (January and February), 67% of their food is grass rhizomes and 25% grass blades (Dunbar, 1977). Geladas are also known to harvest fruits, tubers, and flowers and stems throughout the year. (Dunbar, 1977; Kawai, 1979)

Gelada baboons are highly specialized feeders. The opposability of their first two digits is the highest of all the catarrhine primates and allows them to pick grass blades individually so that they can sort good grass from bad grass during the dry season. It is also notable that their phalanges are short and robust, which allows them to dig efficiently for tubers when desired. These specializations allow gelada baboons to take advantage of grassland environments that other primates could not inhabit as successfully (Dunbar, 1977).

Details on predation of gelada baboons are not available in the literature. Possible predators of these animals include large carnivores and raptors.

As grass feeders, gelada baboons are likely to have significant effects on the plant communities in areas where they feed. By digging for roots, tubers, and grass rhizomes, these animals help to aerate the soil. As possible prey items, these baboons may impact predator populations.

Past records show that gelada baboons were hunted for food by farmers during dry seasons (Jablonski, 1993).

As human populations in Ethiopia and Eritrea grow, city boundries are expanding. Gelada baboons have been blamed for raids on cultivated lands, but many people believe the blame ill-placed. (Kawai, 1979. Jablonski, 1993).

The status of gelada baboons does not appear to be cause for concern at this point, yet because this is such an ecologically specialized species it has been included in the IUCN red Data Book and listed in appendix II of CITES, permitting only monitored trade between countries. Within Africa geladas are "permited to be hunted, killed, or collected only on government authority, but only providing it is in the national interest or for the purpose of science" (Dunbar, 1993: 582). Where geladas have been accused of raiding locally cultivated lands they are shot by farmers (Kawai, 1979). Within the Semien Mountain National Park, which is a conservation area, geladas are completely protected.