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


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January 1994


Low β15N values of Würmian cave bear (Ursus spelaeus) bone collagen indicate a strictly vegetarian diet, and negative δ13C values suggest a forested habitat. Tooth collagen δ15N 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 δ15N values are not reliable for adult diet reconstruction. Tooth collagen δ13C 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 δ13C and δ15N values of several individuals from one locality. Enamel carbonate hydroxylapatite δ13C 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 δ13C 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.

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Palaeogeogr Palaeoclimatol Palaeoecol, Vol. 107, no. 3,4 (1994).