DIETARY VARIATION IN ARCTIC FOXES (ALOPEX-LAGOPUS) - AN ANALYSIS OF STABLE CARBON ISOTOPES

We used stable carbon isotopes to analyse individual variation in arct ic fox diet. We extracted collagen from bones (the lower jaw), and mea sured stable carbon isotopes. The foxes came from three different loca lities: Iceland, where both microtines and reindeer are rare; west Gre enland, where microtines are absent; and Sweden, where seat analyses s howed the primary food to be microtine rodents and reindeer. The Icela ndic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample fro m coastal sites. The spatial variation in the isotopic pattern followe d a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had delta(13)C values of -21.4 (Ice lan d) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14. 9 parts per thousand, whereas coastal foxes from Iceland had intermedi ate values of -17.7 parts per thousand. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was r elated to the availability of different food items. These results were in accordance with other dietary analyses based on seat analyses. Thi s is the first time that stable isotopes have been used to reveal indi vidual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.