Abstract: The guanaco (Lama guanicoe) is the dominant herbivore and undoubtedly one of the most important species for ensuring the health of South American arid ecosystems. Today less than 2% of their original number remains, and populations are highly fragmented. The conservation of this species was one of the main reasons for the creation of the Provincial Reserve La Payunia (southern Mendoza Province, Argentina) in 1982. A great number of livestock graze in the Reserve and its area of influence. This could represent an important threat for guanaco populations, as was previously demonstrated for the Patagonia region. This project proposes to analyze the influence of livestock and productivity on patterns of distribution and density of guanaco (analyzed under Landscape Species Approach, Redford et al. 2000) in space and time. Methods will attempt to link ecological and social variables. Results will be used to develop an integrated management model, and will contribute to decision making about the management of the protected area.