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

We compared over-winter body temperature (T sub(b)) 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 T sub(b) patterns across elevations, with lower elevation populations entering more shallow and infrequent torpor than prairie dogs at higher elevations. T sub(b) 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.