Frank 9728962 The ecological limitations on successful hibernation and subsequent over-winter survival by small mammals are poorly understood. How natural selection influences the evolution of hibernation is thus unknown. Recent laboratory studies with 8 rodent species and 2 marsupials have revealed that the level of unsaturated fatty acids in the diet detE:D~dne; the hibernation ability of small mammals. In these studies, it was found that there is an optimal level of linoleic acid (a polyunsaturated fatty acid) that must be present in the diet for maximal hibernation ability, above or below which hibernation performance is greatly compromised. It has also been shown that high levels of oleic acid (a monounsaturated fatty acid) are also required in the diet for proper hibernation. Mammals can synthesize ~K~K~nrirburabed fatty acids, but they are incapable of synthesizing polyunsaturated fatty acids. Although the biochemical basis of this influence of dietary fatty acids on hibernation ability unknown, it is quite clear that these findings have strong ecological implications which may explain the biogeographical distribution of hibernating mammals, and the role of dietary specialization in the evolution of hibernation. Despite this potential, there have been no studies to date examining how the natural diets of hibernating mammals vary in fatty acid composition, or how this affects over-winter survival under natural conditions. The PI predicts that dietary fatty acid composition influences the over-winter survival of free-ranging S. lateralis, and that this influence is more pronounced in areas where the hibernation period is longer. These hypotheses will be tested in field and laboratory studies involving S. lateralis from the White Mountain of California. This will be the first study to examine the relationship between dietary fatty acid composition and the over-winter survival of a free-ranging hibernator.
