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Hunting strategies and landscape use of past human groups were likely shaped by the seasonal mobility of prey taxa, such as reindeer. It is therefore crucial to reconstruct the movement palaeoecology of these species to understand past human behaviour. Recent developments in isotope techniques offer the tools to study past mobility. Strontium (87Sr/86Sr) isotope can be used to assess the geographic origin of archaeological and palaeontological remains. By targeting tissues that develop incrementally such as tooth enamel, 87Sr/86Sr analyses can be used to determine migratory behaviour and to assess potential seasonal ranges. However, to identify possible migratory pathways, new approaches linking intra-tooth 87Sr/86Sr profiles to 87Sr/86Sr isoscapes are needed. We developed an isoscape-based model, the PleistoHERD model, to assess the distribution and the seasonal movements of Rangifer from their intra-tooth 87Sr/86Sr isotope data using modern caribou data from the Western Arctic herd (Alaska, USA) and the Rivière-aux-Feuilles herd (Québec, Canada). High resolution 87Sr/86Sr sampling profiles of the 2nd and 3rd molars of the individuals were obtained by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Variations in the 87Sr/86Sr isotope profiles of most of the individuals reflected their migratory behaviour during their first 18th month of life. We performed a Bayesian spatial assignment of the endmembers of the profiles to identify potential seasonal ranges and we generated a distribution map time-series for each caribou, using their intra-tooth profile. Caribou movements were then modelled throughout the distribution map times-series accounting for topography and hydrography. As a case study, we applied the model to archaeological reindeer data from France, contrasting seasonal movements of resident and migratory individuals. The interdisciplinary approach we developed, combining isotope analysis, isoscape mapping and animal movement modelling, will allow us to better understand the movement ecology of past ungulates and, consequently, how past humans used their landscape.

EAA 2022: Abstract

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