AbstractHibernators save energy during winter by expressing torpor bouts characterized by strongly reduced body temperature and metabolic rate. Polyunsaturated fatty acids (PUFAs), specifically n-6 PUFAs, are known to positively affect hibernation performance and thereby energy savings predominantly in fat-storing hibernators. Accordingly, hibernators usually retain PUFAs and mobilize monounsaturated fatty acids (MUFAs) or saturated fatty acids (SFAs) during hibernation. In food-storing common hamsters (Cricetus cricetus), however, we previously found that PUFA proportions in white adipose tissue (WAT) decreased during winter, indicating that individuals did mobilize PUFAs. To further investigate these patterns, we analyzed PUFA changes in WAT during hibernation as well as hibernation performance in free-ranging and captive common hamsters with lower prehibernation PUFA proportions compared to those in the previous study. Under controlled conditions, total PUFAs, n-6 PUFAs, and SFAs increased while n-3 PUFAs and MUFAs decreased during hibernation. Higher prehibernation n-6 PUFA proportions resulted in fewer torpor bouts and less time spent in torpor. In free-ranging hamsters, n-6 PUFAs increased while n-3 PUFAs and SFAs decreased during winter. Prehibernation n-6 PUFA proportions, however, did not affect hibernation performance. In summary, these results indicate that the mobilization or retention of n-6 PUFAs during hibernation could depend on their availability in WAT or in the diet before the onset of the hibernation period.