| Abstract: |
An important article that explains the uses of carbon and nitrogen isotopes and also listed the ratios for more than 100 animals repsenting 66 species of birds, fish, and mammals. It has been shown that delta<sup>15<\sup>N and delta<sup>13<\sup>C values of animal tissues are, respectively, about 3 and 1 more positive than those of the animals' diets. This study decided to use bone collagen because its istopic composition reflects that of the animal's diet, its chemistry is well defined, and its amino acid composition varies only slightly between species. Additionally, the choice of bone collagen allows analysis of the remains of animals from prehistoric and earlier periods if the bones still contain collagen. \bNitrogen\b Results indicate that there is a discrete difference between the delta<sup>15<\sup>N values of bone collagen from animals feeding in the terrestrial system and those feeding in the marine system. In sum, the delta<sup>15<\sup>N values of animals feeding exclusively in the marine environment range from +9.4 to +23 with a mean delta<sup>15<\sup>N value of +14.8 #2.5. When all marine animals are considered, fish eaters have a mean delta<sup>15<\sup>N value of +16.5 # 1.9, whereas those animals that do not feed on fish have a mean delta<sup>15<\sup>N value of +13.3 #1.7. Results indicate that the delta<sup>15<\sup>N values of bone collagen from most marine animals are more positive than those for terrestrial animals. \bCarbon\b The delta<sup>13<\sup>C from marine animals are less negative than those from terrestrial animals. Pure marine feeders (-13) and pure terrestrial feeders (-20). The one exception is marine birds. In cases in which the animals are known to use both marine and terrestrial food sources, it should be possible to use delta<sup>15<\sup>N values of bone collagen to estimate general proportions (although not exact percentages) of dependence on marine and terrestrial foods. In geographical areas or within animal populations for which C\-4\- plants are known to be unimportant, delta<sup>13<\sup>C values of bone collagen are useful in estimating dependence on marine versus terrestrial food sources.
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