δ 13C and δ 15N variation on guanacos in Tierra del Fuego: references for terrestrial foodwebs in a high-latitude island

Abstract

The guanaco (Lama guanicoe) was a key staple hunted by foragers throughout the Holocene in southern South America. Stable isotope analyses provide insights about guanaco long-term ecology. Particularly, the characterization of prey habitat and feeding behavior in the past is of the utmost interest for zooarchaeological models. Therefore, we evaluate δ13C and δ15N variation in guanacos inhabiting different C3 plant communities in Tierra del Fuego (Argentina). δ13C and δ15N values derived from bone collagen samples (n = 60), both archeological and modern, serve as geographical markers of forest-steppe environments during the late Holocene. Increased isotopic variation in the middle Holocene could be related either to variations in the terrestrial baseline or to changing dietary behavior of guanacos in a fluctuating environment. Measures of isotopic variability did not clearly correlate to hunting strategies, since areas with similar patterns in the exploitation of guanacos show differences in their isotopic niche size and distribution. Among the samples from the southern coast, there is a strong negative correlation between δ13C and δ15N. This is a trend not observed in herbivores from the forests of continental Patagonia, suggesting that different factors structure natural isotopic variation in guanacos from the Fuegian forest. δ13C and δ15N variation on bone assemblages probably reflect that guanacos fed in confined home-ranges, as it is observed in modern populations, and that hunting activities were developed at patches relatively close to the sites.