Spatial variation of guanaco ( Lama guanicoe ) densities influenced by natural and anthropogenic variables in Southern Andean Precordillera (Argentina)

Abstract

The spatial distribution of ungulate densities is determined by their decisions on habitat selection, modulated by environmental characteristics and human activities. Poaching and habitat degradation are threats to the guanaco, a native herbivore of arid environments of South America. Seasonal surveys of guanacos were carried out during two independent years in mountain environments of Andean Precordillera, inside a protected area and surroundings. Field surveys and GIS analyses estimated environmental variables. Density surface models estimated spatial distribution of guanacos, based on predictions about food availability, weather, risk perception, and human activities. The current distribution of densities is mainly influenced by the availability of preferred food and water, and protection effectiveness. Twelve years ago, disturbing human activities were also relevant. High densities in great altitudes yearlong, and a winter expansion through lower altitudes, are evidence of partial migrations, related to climatic events and food declines. Selective use of Puna grasslands and association with wetlands agree with food and risk predictions. Greater densities inside than outside the protected area, and decreasing guanaco-observer distances, are evidence of continued effective protection. Density surface modeling, applied to multi-year distance sampling, highlights as a useful tool for understanding the spatial dynamics of guanaco populations, and aiding management decisions.