Demography and population dynamics of South American fur seals

Abstract

The demography and population dynamics of South American fur seals, Arctocephalus australis, at Isla de Lobos, Uruguay, were examined. Age-specific rates of survival of females were estimated during four harvest periods (1987, 1988, 1990, and 1991). The estimated continuous and finite rate of population growth (r = 0.021 and λ = 1.021, respectively), obtained from an estimation of abundance of pups was about equal to the value obtained from a matrix model (λ = 1.014). South American fur seals at Isla de Lobos had the highest rates of survival of adults between 1.5 and 2.5 years. Senescence in the age-specific rates of reproduction was determined. The high rates of survival of young females may be the most important life-history parameter in determining the rates of population growth. Fur seals, as other large mammals, appear to have life histories characterized by high rates of survival of adults and low effects of reproduction on growth rates of populations.