Dietary ecology of extant guanaco (Lama guanicoe) from Southern Patagonia: seasonal leaf browsing and its archaeological implications

• Mesowear and microwear study of a monospecific assemblage of extant guanacos.
• Guanacos from the Cardiel Lake area are seasonal mixed feeders.
• Tooth microwear indicates seasonality in the diet of guanaco in Patagonia.
• New proxy for detecting seasonality in archaeological sites in arid environments.

The analysis of dietary traits of ungulates through tooth microwear and mesowear has been applied to archaeological sites to investigate seasonal changes in settlements by hunter–gatherers. In this paper we propose to test the hypothesis that tooth microwear (combined to mesowear) is able to indicate seasonality in the diet of extant ungulates in arid habitats (semi-deserts or steppe). The material analyzed comes from six faunal monospecific assemblages of guanaco (Lama guanicoe) resulting from a mass mortality event in winter 2000 near the Cardiel Lake in Southern Patagonia (Province of Santa Cruz, Argentina). Mesowear results indicate that the guanacos from the Cardiel Lake area are mixed feeders, and thus, have a diet that shifts seasonally. Moreover, microwear analysis supports the hypothesis that tooth microwear is able to indicate seasonality in the diet of extant guanaco in arid habitats. The pattern is clear for the winter sample and needs to be confirmed for a summer sample. Consequently, tooth microwear is proposed as a new potential proxy for detecting seasonal occupation in archaeological sites in Patagonia and other arid environments.