Chemical and carbon isotopic composition of fatty acids in adipose tissue as indicators of dietary history in wild arctic foxes (A lopex lagopus) on Svalbard

The chemical and carbon isotope compositions of triacylglycerol fatty acids were analysed in samples from two or more adipose depots dissected from adult and subadult arctic foxes collected between November 1991 and March 1992 in four different areas of Spitsbergen in the Svalbard archipelago (latitude 78° 5' to 79° 50' N). Site-specific differences were minor but there were large and consistent differences in the fatty acid composition of the storage lipids of foxes caught in the same areas, suggesting that residents of contiguous territories may have had quite different diets. The adipose tissue of adult foxes caught in Austfjordneset, an area where reindeer are rare, contained a much greater proportion of unsaturated fatty acids, suggesting that these animals were feeding mainly in the marine ecosystem, probably on seabirds and/or fish in summer and the remains of polar bear kills in winter. Measurements of the relative abundance of the carbon isotopes ¹²C and ¹³C in individual fatty acids show that palmitoleic acid (C16:1) in storage triacylglycerols originates from the marine food chain, probably together with most other unsaturated lipids, but that the foxes obtain oleic acid (C18:1), and probably most saturated fatty acids, from either terrestrial or marine sources.