Abstract

Hibernating mammals, such as the Long-Tailed Ground Squirrel (*Urocitellus undulatus*), exhibit remarkable physiological adaptations to survive prolonged periods of torpor and low body temperature. A critical component of this adaptation is the precise regulation of lipid metabolism, particularly within skeletal muscle, which must maintain function despite metabolic suppression and disuse. This study investigated the seasonal changes in total fatty acid content and composition in the skeletal muscle of *U. undulatus* to elucidate the biochemical mechanisms supporting muscle integrity and function during the hibernation cycle. Comparative analysis of muscle tissue between the active (summer) and hibernating (winter) states revealed a significant increase in total fatty acid content in winter, particularly in key locomotor muscles such as the quadriceps femoris and triceps. Furthermore, a shift towards a higher proportion of unsaturated fatty acids, notably polyunsaturated fatty acids (PUFAs), was observed. This compositional change is hypothesized to be a vital strategy for maintaining optimal cell membrane fluidity and function at the low body temperatures experienced during torpor, thereby preventing cold-induced muscle damage and ensuring rapid arousal. These findings underscore the essential role of dynamic fatty acid remodeling in the skeletal muscle's successful adaptation to the extreme physiological demands of hibernation.