Song X, Körtner G, Geiser F
Department of Zoology, School of Biological Sciences, University of New England, Armidale, NSW, Australia.
Physiol Behav. 1998 Jul;64(5):675-82. doi: 10.1016/s0031-9384(98)00136-x.
Many small mammals display daily torpor to minimize energy expenditure during the rest phase when faced with unfavorable environmental conditions. However, given a choice of thermal environments, it is not clear whether these daily heterotherms select ambient temperatures that minimize metabolic rates during torpor or ambient temperatures that minimize metabolic rates during normothermia. It is also not clear whether they prefer being normothermic or torpid. In this study, we investigated temperature selection, activity patterns, body temperature patterns, and the use of torpor in Sminthopsis macroura in a thermal gradient when food was freely available or restricted. Animals employed torpor regularly immediately after cessation of activity even when excess food was provided. Nevertheless, they selected high ambient temperature near the zone of thermoneutrality during both normothermia and torpor. Reduced food supply did not affect either temperature preference or total activity, but it did result in significantly prolonged torpor bouts. In addition, it lowered the daily minimum body temperature during torpor by about 2 degrees C. Our study shows that S. macroura selected a high ambient temperature to reduce energy costs during normothermia. Nevertheless, daily torpor was frequently employed at the high temperature, especially when food was restricted.
许多小型哺乳动物在面对不利环境条件时，会在休息阶段进入每日蛰伏状态以尽量减少能量消耗。然而，在有多种热环境可供选择的情况下，尚不清楚这些每日变温动物是选择能使蛰伏期间代谢率降至最低的环境温度，还是选择能使正常体温期间代谢率降至最低的环境温度。也不清楚它们更喜欢保持正常体温还是处于蛰伏状态。在本研究中，我们调查了在食物可自由获取或受限的情况下，粗尾袋鼬在热梯度环境中的温度选择、活动模式、体温模式以及蛰伏的使用情况。即使提供了过量食物，动物在停止活动后仍会立即定期进入蛰伏状态。尽管如此，它们在正常体温和蛰伏期间都选择了接近热中性区的较高环境温度。食物供应减少既不影响温度偏好也不影响总活动量，但确实导致蛰伏时间显著延长。此外，它使蛰伏期间的每日最低体温降低了约2摄氏度。我们的研究表明，粗尾袋鼬选择较高的环境温度以在正常体温期间降低能量成本。然而，即使在高温下，尤其是在食物受限的情况下，仍频繁使用每日蛰伏。
