THE CARBON ISOTOPIC COMPOSITION OF INDIVIDUAL FATTY-ACIDS AS INDICATORS OF DIETARY HISTORY IN ARCTIC FOXES ON SVALBARD

We have measured the carbon isotopic compositions of individual fatty acids isolated from the adipose tissue of arctic foxes (Alopex lagopus ) from the island of Svalbard on the Spitsbergen archipelago to examin e whether dietary sources can be distinguished in the fatty acid isoto pic signature. The diets of Svalbard arctic foxes are unusual in that some members of the population are believed to feed largely in the ter restrial food chain while others feed mainly from the marine food chai n. Isotopic data were obtained for the five major fatty acids present (16:0, 16:1, 18:0, 18:1, and 20:1). A wide range in delta(13)C values for specific fatty acids in Arctic foxes is observed and the mixing li nes produced by the correlation in delta(13)C of the 16- and 18-carbon fatty acids indicate that both marine and terrestrial dietary sources determine fatty acid isotope composition. The differences in delta(13 )C values between marine and terrestrial organisms appear to be passed on to individual fatty acids. The abundance and isotopic composition of 16:1 indicates that the foxes derive this acid from marine sources, whereas, 16:0 and 18:0 appear to have predominantly terrestrial sourc es.