Summary

1. Gelada live in a multi-level social system consisting of at least three increasingly inclusive groupings (coalitions, reproductive units and bands).

2. The basic social group is the one male reproductive unit, consisting of a single breeding male and up to 12 reproductive females, plus their dependent young. Some units contain additional adult males.

3. Reproductive units consist of a number of longterm alliances between two to three reproductive females and their dependent offspring, and these constitute the lowest grouping level in gelada society. Reproductive units that share a common ranging area are termed a band. The band is a relatively closed social unit.

4. Although gelada have low reproductive rates, mortality rates are so low that population growth rates are among the highest recorded for any primate population.

5. The cohesion of reproductive units through time is mainly a function of the relationships among the reproductive females. Males are relatively peripheral, being used as substitute females only by those individuals who lack close relatives with whom to form a more conventional alliance.

6. Females remain in their natal units throughout their lives. Males leave their natal units as subadults to join an all-male group; some two to four years later, they return to the reproductive units to acquire their own breeding females.

7. Males can pursue two main options for acquiring breeding females: they can either (a) take over an entire unit intact after challenging a haremholder or (b) join a unit as a submissive follower in order to build up a nuclear unit-within-a-unit with one or two of the socially more peripheral females.