Viability of the southern elephant seal population of the Falkland Islands

Accurate long-term series of demographic data are available for most popula tions of southern elephant seals. However, research on the elephant seals o f the Falkland Islands began only recently, and information for an accurate forecasting of the future of this population is lacking. In this paper we present data on the current status of the population and its trend in size during the last Il years. We built an age-structured model of the populatio n and analyzed the effect of variation in demographic parameters on populat ion growth. Elasticity analysis demonstrated that variation in mortality ha s a more pronounced effect on instantaneous growth rate than an equivalent variation in fecundity. We examined the effects of environmental variabilit y, inbreeding and catastrophes on population viability by a computer simula tion using the VORTEX PVA programme. In the stochastic model, the most impo rtant factor affecting extinction risk was variability in mortality rates, in particular of the adult classes. We concluded that, although the populat ion does not appear to be at immediate risk of extinction, its small size a nd isolation make it necessary to accurately monitor the population trends and to acquire additional information on life history and feeding strategie s.