We present stable isotopic data obtained in order to elucidate the diet of current domestic camelids and their feeding areas, as a necessary step for the interpretation of archaelogical assemblages, and to answer questions regarding past diet, herd structure, foraging zones and interaction with human populations. Seventeen new δ13C collagen isotope values from Lama glama bones were measured in order to start a systematic study of the isotopic ecology of herbivory in the Puna ecosystem of Jujuy province, Argentina. These values were compared with those previously available, and a reliable correlation between altitude and variation in isotopic values was found: of the order of −2‰ depletion for each 500 m increase in altitude. These results were interpreted as related to variation in vegetal assemblage due to altitude. We consider that the outcomes of this research exceed the scope of our study area, being important to the Argentine Puna as a whole, and will also contribute to the development of current animal population ecological models applied to the interpretation of archaeological remains. Copyright © 2009 John Wiley & Sons, Ltd.