Management of the Vicuña Vicugna vicugna in Chile: Use of a matrix model to assess harvest rates

Abstract

Some aspects of the population dynamics of the vicuña Vicugna vicugna were studied using census and field data recorded at the Reserva Nacional Las Vicuñas, I Region, northernmost Chile. Census data and mean values of fertility and survival were used to estimate functional classes for growth rate and population trends. The Chilean population of the vicuña is growing at an annual rate of 16·4% and the curve fits an exponential model. Using these data a harvest process was simulated with a Leslie matrix population model (Pielou, E.C. (1974). Population and Community Ecology: Principles and Methods. Gordon & Breach, New York). Fertility and survival for each age-functional class were adjusted according to a compensatory mechanism when fixed harvest rates (10, 12·5 and 15%) were applied for a 20-year period. Harvesting three 'adult' classes at 12·5% of the total population showed that the population level remains stable if it is placed at the half carrying capacity level. This rate yielded an average of 1680 specimens per year. A harvest rate of 15% resulted in a 3% annual decrease of the population size. The importance of fertility and survival estimates is discussed, bearing in mind the need to improve future management plans