Seasonal changes in lipids, diet, and body composition of free-ranging black-tailed prairie dogs (Cynomys ludovicianus)

Black-tailed prairie dogs (Cynomys ludovicianus) enter torpor intermittently during winter in the field but do not hibernate continuously from fall to spring. Previous studies have established that hibernators rely primarily on stored lipids during winter and that the storage of n–6 PUFAs in white adipose tissue (WAT) is required to maintain low body temperatures during this continuous torpor. Adult (>1 year) black-tailed prairie dogs were livetrapped in the fall, winter, spring, and summer (n = 10–12). To determine whether free-ranging black-tailed prairie dogs rely heavily on stored proteins during winter, we investigated seasonal changes in body composition of the prairie dogs with dual-energy X-ray absorptiometry scans. We also examined seasonal changes in lipid composition of the WAT and diet using gas–liquid chromatography to determine whether black-tailed prairie dogs lack the lipids necessary for hibernation. Seasonal changes in fat, lean, and total body mass indicate that black-tailed prairie dogs relied heavily on stored lipids during the winter and appeared to rely on proteins primarily during periods that coincided with reproductive activity. Seasonal changes in dietary and WAT lipids indicate that WAT n–6 PUFAs are used during winter and stored during summer, while WAT n–3 PUFAs are stored during winter and used during summer. These patterns of lipid use are different than those reported in free-ranging hibernators and may explain why black-tailed prairie dogs experience shallow and infrequent torpor bouts.