CARBON AND OXYGEN ISOTOPE VARIATION IN TUSK DENTIN OF A FEMALE AMERICAN MASTODON

Patterns of variation in the isotopic composition of mastodon tusk dentin offer information regarding environmental conditions and individual life history. Carbon and oxygen isotope values from the structural carbonate of tusk dentin hydroxyapatite indicate seasonal change and aspects of diet, nutritional stress, and possibly lactational history. Few studies have examined life histories of female mastodons using isotopic composition. One of these studies examined four female mastodons from the Hiscock site (late Pleistocene, eastern New York) during a ca. three-year period near the time of death. A significant short-term rise in both oxygen and carbon isotopic values was observed in the animals sampled, which was hypothesized to be caused by lactation. We attempted to test this hypothesis by sampling another female mastodon (from the Powers site, southwestern Michigan) over a longer interval of time during middle adulthood. Variations in tusk growth rate suggest that this individual gave birth several times during the sampling interval. Preliminary results show strong seasonal patterns in oxygen isotope values consistent with previous studies. Carbon isotope values follow a seasonal pattern interpreted as fat storage and use. The mean carbon isotope value is within the range suggesting a C₃ diet. However, the results are inconclusive regarding identification of a lactational signature. Resampling at higher resolution should allow us to confirm or rule out isotope excursions comparable to those observed in female mastodons from the Hiscock site.