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Theropithecus geladagelada baboon

By Cortney Hiller

Geographic Range

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.

Habitat

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)

  • Range elevation
    2,000 to 5,000 m
    to ft

Physical Description

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)

  • Sexual Dimorphism
  • male larger
  • Range mass
    13 to 21 kg
    28.63 to 46.26 lb
  • Range length
    50 to 74 cm
    19.69 to 29.13 in

Reproduction

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.

  • Breeding interval
    It is possible for a female to produce young annually under good conditions.
  • Breeding season
    Gelada baboons do not have a specific mating season, though it has been noted that the birth rate is higher during the rainy season.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    5 to 6 months
  • Range weaning age
    12 to 18 months
  • Range age at sexual or reproductive maturity (female)
    4 to 5 years
  • Range age at sexual or reproductive maturity (male)
    5 to 7 months

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.

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • extended period of juvenile learning

Lifespan/Longevity

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.

Behavior

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).

Communication and Perception

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.

Food Habits

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).

  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

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

Ecosystem Roles

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.

Economic Importance for Humans: Positive

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

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

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).

  • Negative Impacts
  • crop pest

Conservation Status

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.

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Cortney Hiller (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

polygynous

having more than one female as a mate at one time

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

Dunbar, R. 1977. Feeding Ecology of Gelada Baboons: A Preliminary Report. Pp. 252-273 in T Clutton-Brock, ed. Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and Apes. London: Academic Press.

Dunbar, R. 1993. Conservation Status of the Gelada. Pp. 527-531 in N Jablonski, ed. Theropithecus: The Rise and Fall of a Primate Genus. Great Britain: Cambridge University Press.

Dunbar, R. 1987. Demography and Reproduction. Pp. 240-249 in B Smuts, D Cheney, R Syefarth, R Wrangham, T Struhsaker, eds. Primate Societies. Chicago: The University of Chicago Press.

Jablonski, N. 1993. Introduction. Pp. 3-15 in N Jablonski, ed. Theropithecus: The Rise and Fall of a Primate Genus. Great Britain: Cambridge University Press.

Kawai, M., F. Szalay. 1979. Ecological and Sociological Studies of Gelada Baboons. Contributions to Primatology, 16.

Smuts, B. 1987. Sexual Competition and Mate Choice. Pp. 385-394 in B Smuts, D Cheney, R Seyfarth, R Wrangham, T Struhsaker, eds. Primate Societies. Chicago: The Univerisity of Chicago Press.

Stammbach, E. 1987. Desert, Forest, and Montane Baboons: Multilevel-Societies. Pp. 112-120 in B Smuts, D Cheney, R Seyfarth, R Wrangham, T Struhsaker, eds. Primate Societies. Chicago: The University of Chicago Press.

Wrangham, R. 1987. Evolution of Social Structure. Pp. 282-296 in B Smuts, D Cheney, R Seyfarth, R Wrangham, T Struhsaker, eds. Primate Societies. Chicago: The University of Chicago Press.

van Hooff, J. 1990. Macaques and Allies. Pp. 208-286 in S Parker, ed. Grzimek's Encycolpedia of Mammals. New York: McGraw-Hill Publishing Company.

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