Stable isotopes (δ ¹³ C and δ ¹⁵ N) from archaeological rodent bones support the Holocene distribution of caviomorphs in the Patagonian Andean Fores

The presence of caviomorph and ctenomid rodents in the Patagonian Andean Forest during the Holocene—beyond their present-day distribution, largely restricted to the steppe and steppe–forest ecotone—raises interpretive challenges. These concerns relate to the palaeoecological implications of the discrepancy between current and past distributions, as well as their potential involvement in human subsistence strategies, given the persistence of forests in this region since the Pleistocene–Holocene transition. Stable isotope analysis is a valuable approach to addressing these issues, as nitrogen isotope values in faunal and human assemblages have been shown to reflect forest resource use in Patagonia. We analysed δ ¹³ C and δ ¹⁵ N values in caviomorph rodent remains from the Población Anticura archaeological site, which is located within the Andean forest, around 40 km from the steppe. The assemblage includes multiple caviomorph taxa distributed across five archaeological units spanning from the Early Holocene to historical times, providing a diachronic perspective on isotopic variability. The specimens yielded mean δ ¹³ C values of −22.1‰ ± 0.6‰ and δ ¹⁵ N values of 2.0‰ ± 0.95‰. These results were then compared with isotopic data from steppe rodents, as well as from cervids ( Hippocamelus bisulcus and Pudu puda ), which serve as ecological references for forest environments. This comparative analysis confirms an association between the Población Anticura rodents and an isotopic signal derived from the forest, highlighting the effectiveness of stable isotopes in assessing the interaction between human groups and different species in forest landscapes in northwestern Patagonia during the Holocene.