VARIATION IN TORPOR PATTERNS OF FREE-RANGING BLACK-TAILED AND UTAH PRAIRIE DOGS ACROSS GRADIENTS OF ELEVATION

We compared over-winter body temperature (Tb) patterns for more than 6 months in adult (>1 year) black-tailed (Cynomys ludovicianus) and Utah (C. parvidens) prairie dogs from colonies located along gradients of elevation in northern Colorado and southern Utah. In general, black-tailed prairie dogs entered torpor facultatively during winter, whereas Utah prairie dogs hibernated continuously for extended periods. Both black-tailed and Utah prairie dogs displayed significant differences in Tb patterns across elevations, with lower elevation populations entering more shallow and infrequent torpor than prairie dogs at higher elevations. Tb patterns of black-tailed prairie dogs followed 24-h cycles, as most prairie dogs entered into and aroused from torpor between 1100 and 1700 h and bout lengths were clustered around 24-h intervals and multiples thereof. Torpor in Utah prairie dogs did not display the same daily patterns; they entered into and aroused from torpor at all times of the day, and bout lengths were variable. Although black-tailed and Utah prairie dogs are closely related, mechanisms that stimulate and control torpor might differ between them.