Previous laboratory studies demonstrated profound effects of dietary linoleic acid, a polyunsaturated fatty;acid (PUFA), on hibernation patterns in rodents. We investigated PUFA composition in white adipose tissue (WAT), and possible influences of PUFAs on hibernation in free-living alpine marmots (Marmota marmota). Our results show considerable seasonal and regional variation in WAT fatty acid composition, as well as differences between adipose tissue sites. Further, hibernation body mass loss decreased as WAT linoleic acid content increased. Attenuated winter mass-loss in marmots with high dietary linoleic acid uptake appeared to be partly due to lowered mean gradients of body to ambient temperatures during deep hibernation. We conclude that local variability in dietary PUFA availability may be high enough to result in significant energetic consequences for free-ranging hibernators.