Data on population size, density and composition, biomass, group size and composition and reproductive rates are compared between populations in the two regions of gorilla
distribution, equatorial west and east central Africa. The Virunga Volcano population of the latter region is shown to be a good model for all populations. Information on age at maturity, birth rates, mortality rates of adults and immatures and migration of individuals within the population is presented but data are available only for the Virunga population. The significance of a knowledge of the pattern of migration of individuals to the genetic consequences of large reduction in population size is stressed.