DIET, PHYSIOLOGY AND ECOLOGY OF FOSSIL MAMMALS AS INFERRED FROM STABLE CARBON AND NITROGEN ISOTOPE BIOGEOCHEMISTRY - IMPLICATIONS FOR PLEISTOCENE BEARS

Low delta(15)N values of Wurmian cave bear (Ursus spelaeus) bone colla gen indicate a strictly vegetarian diet, and negative delta(13)C value s suggest a forested habitat. Tooth collagen delta(15)N values are abo ut 2 parts per thousand higher than bone collagen within one individua l, similar to that found in the modern black bear (UI sus americanus). These data suggest an influence of a N-15-enriched milk diet during t he synthesis of tooth collagen, which is partly formed before weaning. Thus, tooth collagen delta(15)N values are not reliable for adult die t reconstruction. Tooth collagen delta(13)C values are around 1 parts per thousand lower than bone collagen, suggesting a C-13- depleted mil k diet. A similar pattern of variation is seen in the average delta(13 )C and delta(15)N values of several individuals from one locality. Ena mel carbonate hydroxylapatite delta(13)C values are low in cave bears (around -14 parts per thousand) when compared to carnivores (around -1 2 parts per thousand) and herbivores (-10 parts per thousand). This is probably due to lipid use while hibernating during winter. A similar pattern of enamel carbonate hydroxylapatite delta(13)C values differen ces 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.