Guanacos and isotopic ecology in northern Neuquen: The record from Cueva Huenul 1

Abstract

In this work we present the first systematic results about regional isotopic ecology in northern Neuquén Province (Argentina). This information is essential to reconstruct ecological changes and human paleodiets through time. We conducted analyses of stable isotopes of carbon (13C/12C) and nitrogen (15N/14N) on the collagen fraction of bone from one human sample and 39 faunal samples from archaeological sites in Barrancas-Buta Ranquil locality. The results correspond to five wild species, though analysis is focused in guanaco (Lama guanicoe). The information produced is interpreted in the framework of regional botanical surveys that show the differential abundance of species with different photosynthetic pathways. Due to its position, next to the ecotone between the Monte and Patagonia phytogeographical provinces, the area is a sensitive spot to test ecological changes through time.
The species recorded in the botanical transects follow the C3 photosynthetic pathway. Accordingly, the values produced for faunal samples reveal C3-based trophic chains. The human burial from Buta Có Abajo shows values indicative of a diet based on camelids, which would have also included small animals with higher isotope values. The samples analyzed for guanaco show differences between the early and late Holocene components from CH1, where the more recent assemblage shows a more intense consumption of C3 plants. By integrating data available for neighbor southern Mendoza region, we evaluate regional isotopic patterns associated to altitude and latitude. We do not recorded strong relations between altitude and ?13C and ?15N values. On the other hand, there is a weak latitudinal pattern in ?13C values, which show more depleted values in CH1 compared to settings located further north.