Isotopic insights on cave bear palaeodiet

More than 300 cave bear bones from all over Europe have carbon and nitrogen isotopic composition that match overwhelmingly a diet based on plants, except for samples from two caves in Romania, for which high nitrogen-15 amounts have been interpreted as reflecting an omnivorous diet. This paper aims at deciphering the various factors influencing the carbon and nitrogen isotopic composition of a potential omnivorous species like cave bear, those linked to trophic levels and variations among plants and those caused by physiological factors. The comparison of European cave bears with coeval Late Pleistocene large mammals with different diets clearly shows that all the cave bear populations, including those from Romania, present isotopic values overlapping with herbivores, not with carnivores. Therefore omnivory is very unlikely for cave bears. Consumption of plants with high δ15N values, such as graminoids, forbs and possibly fungi, could explain in part the observed isotopic pattern. In addition, the variations in δ15N values through ontogeny support the hypothesis of a different hibernation pattern for the Romanian cave bears with high δ15N values. Future investigations using new isotopic approaches, especially nitrogen isotopic composition of collagen amino acids, should contribute to decipher the paleoecology of these Romanian cave bears