Species: Theropithecus gelada.

PHYSICAL DESCRIPTION: Male Ht. 2.2 ft., Wt. 50 lbs. Female Ht. 2 ft., Wt. 35 lbs. Coat: brown, turning to cream at ends of long hairs, mane and cape over shoulders, naked area of red skin around base of neck, surrounded by whitish lumps which in females vary in size with the menstrual cycle. Upper lip can be everted, used in "flash" display of canines. Large canines, esp. males. Stubby hands have opposable thumbs useful for picking up small food items such as grass stems and seeds, and are good at digging up roots and tubers. Quadrupedal, although feeding is usually done while sitting. Longevity: about 15 years in wild.


ECOLOGY: Terrestrial foragers. Grasslands. Sleep on cliffs. Home range: 10 km2 Day range: 2 km. Population density: variable, approx. 70 / km2

DIET: Grass, seeds, tubers, bulbs, fruit, insects.

SOCIAL ORGANIZATION: complex hierarchical groups composed of polygynous one-male units, bands, and herds. Foraging groups typically are OMU's, with one adult male and 1-10 females + offspring. Females form life-long coalitions with close maternal relatives (sisters, mothers, ...). Dominant and peripheral females; peripheral females usually determine daily foraging. Bachelor males commonly form all-male groups; solitary males occasionally follow OMU's and attempt to attract some of the younger females away. Male transfer, at least as far as band level; female kin groups. Frequent play among juveniles. Complex social relationships among various levels of social hierarchy. Herds probably serve predator avoidance function.

REPRODUCTION: Males sexually mature at 6 yrs, but unlikely to be successful reproducers until 8+. Females sexually mature at 4-5 yrs. Gestation length: 6 months. Moderate estrus swellings, including chest and neck. Litter size: 1. Interbirth interval: 2 yrs. Infant birth wt.: 3 lbs.

PARENTAL CARE: Infants carried by females for 8 mo. Weaning at 1 yr. Possible occasional male protection?

TOPIC OF SPECIAL INTEREST: Complex social interactions, estrus swellings, coalitions, large goups, complex kinship.


Dunbar, R.I.M. 1984. Reproductive decisions: an economic analysis of gelada baboon social strategies. Princeton: Princeton University Press.

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