Changes in the intramolecular stable carbon isotope ratios with age of the European cave bear (Ursus spelaeus)

Changes with age in the diet and metabolism of the extinct European cave bear (Ursus spelaeus) from the Divje Babe archaeological site in northwestern Slovenia were investigated by comparing the stable carbon isotope ratio of whole bone collagen with that of the peptide-bonded carboxyl carbons in collagen. These carboxyl carbons were selectively released by decarboxylation of the collagen hydrolysate with ninhydrin (2,2-dihydroxy-1,3-indanedione). The stable carbon isotope ratio increased with age for both the peptide-bonded and other carbons. Although only one-third of the carbon atoms in collagen are peptide-bonded, they account for most of the observed change with age of the stable carbon isotope ratio of the whole collagen. Stable nitrogen isotope ratios decreased with age and were negatively correlated with changes in the stable carbon isotope ratios. These observations support previous investigations on the unique metabolism of hibernating bears.