Diet, physiology and ecology of fossil mammals as inferred from stable carbon and nitrogen isotope biogeochemistry: implications for Pleistocene bears

Abstract

Low β 15N values of Würmian cave bear ( Ursus spelaeus) bone collagen indicate a strictly vegetarian diet, and negative δ 13C values suggest a forested habitat. Tooth collagen δ 15N values are about 2% 0 higher than bone collagen within one individual, similar to that found in the modern black bear ( Ursus americanus). These data suggest an influence of a 15N-enriched milk diet during the synthesis of tooth collagen, which is partly formed before weaning. Thus, tooth collagen δ 15N values are not reliable for adult diet reconstruction. Tooth collagen δ 13C values are around 1% 0 lower than bone collagen, suggesting a 13C-depleted milk diet. A similar pattern of variation is seen in the average δ 13C and δ 15N values of several individuals from one locality. Enamel carbonate hydroxylapatite δ 13C values are low in cave bears (around −14% 0) when compared to carnivores (around −12% 0) and herbivores (−10% 0). This is probably due to lipid use while hibernating during winter. A similar pattern of enamel carbonate hydroxylapatite δ 13C values differences is found between Deninger's bear ( Ursus deningeri), carnivores and herbivores in 200,000 to 600,000 year old caves, suggesting a similar physiology for both fossil bear species.