Multi-isotope analysis of bone collagen of Late Pleistocene ungulates reveals niche partitioning and behavioural plasticity of reindeer during MIS 3.

Here we present stable carbon, nitrogen and sulfur isotope ratios of collagen extracted from Rangifer, Equus and Bison bone (n = 128) from different stratigraphic levels at the chronologically well-constrained Middle and Upper Palaeolithic site of Les Cottés, France. Samples were taken from five phases of site use (US08, US06, US04 [upper and lower], and US02; ~ 45.8-35.3 ka cal BP) to explore the dietary and spatial palaeoecology of these ungulate species during MIS 3, and the contemporary climate. Temporal trends in δ ¹⁵ N values of all species broadly align with other climatic indicators at the site and the lowest values in US04 correspond to the Heinrich 4 cooling event, reflecting changes in the composition of soil/plant nitrogen at this time. Rangifer collagen is ¹³ C-enriched compared to the other species throughout, consistent with lichen consumption. However, this isotopic niche partitioning between Rangifer and Equus/Bison is most extensive during US04, indicating plasticity in reindeer feeding behaviour, and potentially overall increased lichen biomass during this cooler/more arid phase. Rangifer δ ³⁴ S values are consistently lower than Equus and Bison, which could be indicative of their more extensive spatial ranges incorporating greater inland areas. Equus and Bison demonstrate a significant decrease in δ ³⁴ S values through time, which may be linked to contemporary climatic decline.
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