The seasonal patterns of nonshivering thermogeneis (NST), resting metabolic rate (RMR) at 15"C and 25"C in plateau pikas Ochotona curzoniae {Hodgson, 1858) and root voles Microtus oeconomus (Pallas, 1776), from the Qinghai-Tibetan plateau, were determined and thermal conductance was calculated. NST tended to increase during cold season for both species. No significant seasonal variations in NST were found in pikas {mean maximum in winter: 3.46 ± 0.19 ml Oa/g-h; minimum in spring: 3.07 + 0,16 ml Ou/g-h). Voles increased NST significantly as the ambient temperature decreased, from the lowest, mean 8.00 ± 0.42 ml Oa/g-h, in summer to the peak in winter, mean 11.29 i 0.44 ml Os/g* h. RJV1R and thermal conductance were lower in winter than those in summer for both species (mean in summer at 25'C: 4.96 + 0.35 ml 02/g-h and 0.509 ± 0.027 ml Oa/g-h-"C for voles and 2.11 ± 0,09 ml Os/g-h and 0.179 ± 0.003 ml Oa/g-h-'C for pikas, respectivly; mean in winter at 25°C: 4.22 ± 0.26 mlOa/g*h and 0.379 ± 0.012 mlCVg-h-'C for voles and 1.55 ± 0.06 ml Oa/g-h and 0.123 ± 0.003 ml Oa/g-h'"C for pikas, respectively). Voles lost body weights in winter whereas pikas kept their body weights. This suggests that alpine small mammals, which have high levels of metabolism and thermal conductance, mainly depend on increasing thermogenic capacities and insulation, decreasing energy expenditure per individual, augmented by behavoral adjustments to cope with cold temperatres of winter.
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