DIET OF THE MOUNTAIN VIZCACHA (LAGIDIUM-VISCACIA MOLINA, 1782) AND FOOD AVAILABILITY IN NORTHERN PATAGONIA, ARGENTINA

Diet of Lagidium viscacia and food availability were seasonally determ ined in La Payunia Protected Area through faecal analysis and point qu adrat transects, respectively, in rocky elevations (shelter of mountai n vizcachas) and adjacent plains. There were several evidences of sele ctive feeding behaviour, besides the little similarity between diet an d availability. The diet included only 33% of the plant genera occurri ng in the environment, the main dietary elements being three grasses ( Poa, Hordeum, and Stipa) and one camephyte (Acantholippia). The propor tion of grasses was significantly higher in the diet than in the envir onment, especially in the shrubby rocky elevations. The main food, Pea , was scarce to absent in rocky elevations, where L, viscacia lives, r epresenting evidence of L, viscacia's descending to plains for feeding . Similar behaviour was detected in L. peruanum and Procavia johnstoni , the rocky hyrax. The plains adjacent to rocky elevations in La Payun ia were inhabited by the plains vizcacha, Lagostomus maximus, a closel y related species to L. viscacia. Considerable similarity between both Chinchillidae diets suggests the possibility of competition, Poa bein g the key dietary element. Feeding behaviour of L. viscacia is focusse d through the central place foraging theory, with rocky elevations as shelter against aerial predators.