Habitat use and selection by the vicuña (Vicugna vicugna, Camelidae) during summer and winter in the High Andean Puna of Argentina

Habitat use and selection by vicuñas and particularly by individuals of different social categories were evaluated during the summer and winter of two years (2006 and 2007) that differed in their precipitation pattern. Both, use and selection, were analyzed within the framework of the optimal foraging theory (OFT) that predicts a high proportion of individuals using habitats where the most nutritional food items are present, and if other things are equal, habitats should be chosen if they yield the highest average rate of energy intake, which fits with this theory. Indeed, a prediction of the habitat selection theory (HST) was evaluated during winter (dry season). Over the study period high proportions of vicuñas occupied habitats with availability of high quality food, which supports the OFT. However, habitat selection differed between seasons and years due to the decrease in plant resource availability in the winter of both years and in the summer of 2007 (with drought conditions). In the dry season of the good year (2006), vicuñas (familial individuals, particularly) were more homogeneously distributed among habitats than in summer, which is consistent with the HST. High proportions of individuals at the wetland (called vega) were more evident during the bad year (2007) than in the good one. Therefore, habitat use (and selection) by vicuñas in this sector of the Puna region is influenced by the availability of high quality food resources and by the presence of water, and the relevance of the latter increased with drought conditions. An assessment of the interactions between individuals of different social categories will contribute to better understanding the distribution of animals among different habitats.