Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies

The isotope enrichment epsilon* of C-13 between tooth enamel of large ruminant mammals and their diet is 14.1 +/- 0.5 parts per thousand. This value was obtained by analyzing both the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment, although our data cannot determine if it is significantly different. We also found a C-13 isotope enrichment epsilon* of 3.1 +/- 0.7 parts per thousand for horn relative to diet, and 11.1 +/- 0.8 parts per thousand for enamel relative to horn for ruminant mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic composition of the atmosphere, determine the fraction of C-3 or C-4 biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C-4 photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats.