Fatty acid composition of the adipose tissue of six carnivorous mammalian species (European otter Lutra lutra, American mink Mustela vison, European Mink Mustela lutreola, European polecat Mustela putorius, stone marten Martes foina and European wild cat Felis silvestris) was studied. These species forage to differing degrees in aquatic and terrestrial food webs. Fatty acid analysis revealed significant differences in polyunsaturated fatty acid composition between species. More specifically, our results underline a gradual significant decrease in the docosahexaenoic acid (DHA)/linoleic acid (LNA) ratio of carnivore species as their dependence on aquatic food webs decreases. In conclusion, the use of the DHA/LNA ratio in long-term studies is proposed as a potential proxy of changes in foraging behaviour of semi-aquatic mammals.