Gelada baboon
Theropithecus gelada

TAXONOMY

Suborder: Haplorrhini
Infraorder: Simiiformes
Superfamily: Cercopithecoidea
Family: Cercopithecidae
Subfamily: Cercopithecinae
Genus: Theropithecus
Species: T. gelada
Subspecies: T. g. gelada, T. g. obscurus

Other names: gelada baboon; gelada (French); gelada (Swedish); T. g. gelada: common gelada, northern gelada, western gelada; T. g. obscurus: dusky gelada, eastern gelada, Heuglin’s gelada, southern gelada.

The gelada is the sole survivor of the genus Theropithecus, which formerly included several extinct species which were widespread and successful, found over much of Africa and into India (see Delson 1993 & Jablonski 1993; Pickford 1993; Dunbar 1998).

MORPHOLOGY

Theropithecus gelada
Photo: Peter Fashing

Geladas are large, stocky primates with dark brown to buff coarse pelage and with dark brown faces and lighter, pale eyelids. The tail is shorter than the body and head and has a tuft at the end (Napier 1981; Ankel-Simons 2007). The forearms and extremities are almost black (Napier & Napier 1967). In adult males, a long, heavy, cape of hair is present on the back (Napier 1981; Ankel-Simons 2007). Between subspecies, T. g. gelada usually has predominantly pale brown to dark brown pelage, while T. g. obscurus is darker, ranging from dark brown to almost black (Yalden et al. 1977). The face has no hair, and is shorter and higher than in other baboons. In addition, the snout is more chimp-like than baboon-like (Ankel-Simons 2007). Most characteristic of geladas is the hairless hourglass-shaped pink or red area of skin located on the chest (Napier 1981; Ankel-Simons 2007). In females, this skin patch is surrounded by pearl-like knobs of skin. Geladas have pronounced ischial callosities (Ankel-Simons 2007). On average, males are larger than females and marked sexual dimorphism is characteristic of the species, with females averaging around two-thirds the size of males (Krentz 1993; Jolly 2007). Females average around 11 kg (24.3 lb) while males weigh 18.5 kg (40.8 lb) (data compiled by Jolly 2007). Head and body lengths of the sexes combined range between 50 and 75 cm (19.7 and 29.5 in) and the tail is between 30 and 50 cm (11.8 and 19.7in) long (Ankel-Simons 2007). The species has highly opposable index fingers and thumbs, the most so of any of the primates (Napier 1981). In addition, its fingers are short and substantially built, allowing them to be used efficiently for digging (Dunbar 1976). Geladas have specialized dentition adapted for their highly graminivorous diet, which is highly abrasive to teeth (Jablonski 1994).

In captivity, geladas have lived into their thirties but the estimated wild life expectancy is less than 14 years (Dunbar 1980a; Weigl 2005).

Geladas are one of the most terrestrial of the non-human primates, and are best described as nearly completely terrestrial quadrupeds with specialized morphological adaptations for feeding and moving on the ground (Dunbar 1983b; 1986; Krentz 1993). As a result of its adaptations, feeding occurs on the ground, with only extremely rare excursions into bushes to access food (Dunbar 1977b). The typical feeding posture and associated locomotion (shuffle gait) is unique to the gelada, and occurs in a sitting position (Dunbar 1977b; 1983). During this type of feeding locomotion, the animal squats, feeds, and shuffles forward bipedally without changing its posture allowing near-continuous foraging and consumption (Wrangham 1980; Dunbar 1983b). Movement of this type occurs frequently throughout the day but usually only over distances of less than one meter. As a result, due to high proportions of time spent feeding, the bipedal shuffle gait can comprise up to a third of the daily locomotor behavior (Wrangham 1980).

RANGE

Geladas are found only in Ethiopia, on the Ethiopian plateau predominantly south of the Tacazze River, north of the Awash River, and east of the Blue Nile River (Dunbar 1993a; Oates 1996). However, a population was found a significant distance from other populations further south along the upper Wabi-Shebeli River, in the Arusi Region (Mori & Belay 1990). In many places, the distribution is discontinuous and the species occurs only very near cliffs and gorges (Dunbar 1993a). Between subspecies, T. g. obscurus is found in the south of the species range, while T. g. gelada is found in the north. They are roughly divided by the gorges of the Belegas and upper Tacazze rivers (Yalden et al. 1977).

The total wild population of gelada baboons is estimated at slightly less than 250,000 individuals (Dunbar 1998).

HABITAT

Geladas are found in open, high plateaus along the gorges and escarpments that dissect them, above 1500 m (4921.3 ft) up to around 4500 m (14763.8 ft) with most populations inhabiting altitudes between 2000 and 3000 m (6561.7 and 9842.5 ft) (Iwamoto & Dunbar 1983; Dunbar 1992; 1993; Iwamoto 1993; Belay & Shotake 1998; Jolly 2007). Gelada habitats are characterized by their proximity to cliffs for sleeping and the use of several different types of relatively treeless and montane grasslands for foraging, habitats that are usually interspersed with bushes, trees and dense thickets (Dunbar 1976; Kawai & Iwamoto 1979; Napier 1981; Iwamoto & Dunbar 1983; Iwamoto 1993; Jolly 2007). Vegetation in study areas usually consists of grasses, herbs, and bush level vegetation. In some habitats, the weather can be harsh, as hailstorms occur regularly in the wet season and frosts are seen in the dry season (Iwamoto & Dunbar 1983). Because certain areas of their plateau habitat are under human cultivation, populations often are marginalized to the areas near the cliffs and sometimes geladas invade the intrusive cropland to forage (Iwamoto 1993). The typical pattern of habitat use is to sleep on cliffs and to climb up to the plateaus for their daily activities, but still remain close to the cliffs (Napier 1981; Iwamoto 1993; Jolly 2007). While usually only cliff faces and nearby grasslands are utilized, when slopes are present in a habitat, they will be used as well (Mori et al. 1999). Gelada habitat is generally cooler and less arid then lowland areas which mitigates the negative effects of the dry season on food availability (Iwamoto 1993).

Theropithecus gelada
Photo: Irwin S. Bernstein

On the Amhara plateau, the year can be divided into rainy (June-September) and dry seasons with more southern habitats showing a slight second rainy season in March and April (Iwamoto 1993). Annual rainfall in gelada habitats is usually around 120 cm (47.2 in) but usually increases with altitude (Iwamoto & Dunbar 1983; Iwamoto 1993). Monthly average temperatures on the Amhara plateau range from highs around 20°C (68°F ) (March-May) to lows around 15°C (59°F) (July-September) with a general trend towards lower temperatures as the altitude increases (Iwamoto & Dunbar 1983; Iwamoto 1993). Daily however, the temperature may vary by up to 25°C (45°F) and can drop below freezing (Iwamoto & Dunbar 1983).

ECOLOGY

Geladas are best described as predominantly graminivorous and are genuine grazers with over 90% of the diet being grass blades. There is a shift to flowers and digging for rhizomes and roots and foraging for herbs when the availability or nutritional value of available grasses changes (Dunbar & Dunbar 1974b; Dunbar 1976; 1977; Iwamoto & Dunbar 1983; Dunbar 1984b; Iwamoto 1993; Dunbar 1998). Geladas are the only graminivorous primate and consume foods more akin to those eaten by ungulates, chewing food about as efficiently as zebras (Iwamoto 1979; Dunbar & Bose 1991; Iwamoto 1993). They eat both the leaves and seeds of grasses, in addition to herbs, flowers, small plants, fruits, creepers, bushes, thistles, and insects (Dunbar 1976; 1977; Iwamoto & Dunbar 1983; Iwamoto 1993). Insects are only eaten rarely and then only if they are easily attained (Iwamoto 1993). There is a variable seasonal shift in dry season diet in which fewer grasses are consumed and other food plants, especially herbs, are substituted. Further, when grasses are in seed, proportionally more seeds are consumed and they are preferentially chosen over grass blades when both are available (Dunbar 1976; Iwamoto 1993).

The night is spent on cliff faces, sleeping on ledges (Crook 1966). In the morning around sunrise, the diurnal geladas will leave their sleeping cliffs, ascend to the top of the plateau and immediately commence social activities and feeding (Dunbar & Dunbar 1974b; Dunbar 1977b; Iwamoto 1993). After the morning social interaction, feeding increases in incidence and is the main activity for the rest of the day, sometimes punctuated by travel, until the evening when some social activity is seen again prior to descending to the cliff sleeping sites (Dunbar & Dunbar 1974b; Dunbar 1977b). Between several study sites, the day is usually spent feeding (35.7-62.3%), moving (14.7-20.4%), resting (5.2-26.3%), and in social activities (16.0-20.5%) (Iwamoto & Dunbar 1983). However, at some study locations, feeding may consist of up to 81.6% of the time spent during the day with the remainder of the day spent mostly moving and grooming (Kawai & Iwamoto 1979). The active period is between 11-12 hours and during the dry season, more time is spent feeding (Iwamoto 1993). Most of the distance traveled over the course of the day is due to foraging and as habitat altitude increases, feeding time goes up (Dunbar 1977b; Iwamoto & Dunbar 1977; Dunbar 1992). In general between populations, as feeding goes up, resting decreases, and relative to one another, time spent moving and in social interactions stays about the same (Iwamoto & Dunbar 1983).

Theropithecus gelada
Photo: Peter Fashing

Day range varies daily and seasonally but is closely related to group size, with animals ranging between averages of 600-2160 m (1968.5-7086.6 ft) per day with larger groups moving longer distances (Dunbar & Dunbar 1979; Kawai & Iwamoto 1979; Iwamoto & Dunbar 1983). Home ranges vary between about 0.78 and 3.44 km2 (0.3 and 1.3 mi2) and similarly to day range, are related to group size, with larger groups possessing larger home ranges (Iwamoto & Dunbar 1983).

During the rainy season, geladas feed by sitting and foraging with both hands in turn, using their thumb and 1st digit to pick suitably green blades of grass (Crook & Aldrich-Blake 1968; Dunbar 1977b; Iwamoto 1993). The blades are only transferred to the mouth after 10-20 are accumulated in the hand and after several minutes, the gelada will shuffle or walk several meters and continue feeding (Crook & Aldrich-Blake 1968; Dunbar 1977b; Iwamoto 1993). During the dry season, when preferred foods are often under the ground surface, geladas will dig using both hands as shovels (Crook & Aldrich-Blake 1968; Iwamoto 1993).

Other primates with which geladas are often sympatric include baboons (Papio sp.) and vervet monkeys (Chlorocebus aethiops) (Crook & Aldrich-Blake 1968; Dunbar & Dunbar 1979). They are sometimes found in association with baboons but never with vervets. However, because of their specialized diet, they are not in direct food competition with either of these two primate species (Dunbar & Dunbar 1979). On the other hand, also due to their diet, geladas potentially face competition from sympatric, non-primate herbivores, including ibex (Capra walie), klipspringers (Oreotragus oreotragus), bushbucks (Tragelaphus scriptus), duikers (Sylvicapra grimmia) and domesticated horses and cattle (Dunbar 1978a).

Geladas are threatened by several potential and actual predators. These include dogs, jackals, leopards, servals, foxes, hyenas, and lammergeyers (Dunbar & Dunbar 1975; Ohsawa 1979; Iwamoto et al. 1996; Mori et al. 1997). The usual response to predators is to flee to cliff faces, but in some circumstances, males may confront a threat and have even been observed to confront dogs and even mob and surround a leopard (Dunbar & Dunbar 1975; Ohsawa 1979; Iwamoto et al. 1996). In general, predation pressure seems low, likely due to the proximity of humans to many habitats (Iwamoto 1993).

Content last modified: September 3, 2008

Written by Kurt Gron. Reviewed by Robin Dunbar.

Cite this page as:
Gron KJ. 2008 September 3. Primate Factsheets: Gelada baboon (Theropithecus gelada) Taxonomy, Morphology, & Ecology . <http://pin.primate.wisc.edu/factsheets/entry/gelada_baboon/>. Accessed 2013 May 24.