Milling Charlotte R, Rachlow Janet L, Chappell Mark A, Camp Meghan J, Johnson Timothy R, Shipley Lisa A, Paul David R, Forbey Jennifer S
Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, USA.
School of Environment and Natural Resources, Ohio State University, Columbus, OH, USA.
PeerJ. 2018 Mar 16;6:e4511. doi: 10.7717/peerj.4511. eCollection 2018.
Small mammals in habitats with strong seasonal variation in the thermal environment often exhibit physiological and behavioral adaptations for coping with thermal extremes and reducing thermoregulatory costs. Burrows are especially important for providing thermal refuge when above-ground temperatures require high regulatory costs (e.g., water or energy) or exceed the physiological tolerances of an organism. Our objective was to explore the role of burrows as thermal refuges for a small endotherm, the pygmy rabbit (), during the summer and winter by quantifying energetic costs associated with resting above and below ground. We used indirect calorimetry to determine the relationship between energy expenditure and ambient temperature over a range of temperatures that pygmy rabbits experience in their natural habitat. We also measured the temperature of above- and below-ground rest sites used by pygmy rabbits in eastern Idaho, USA, during summer and winter and estimated the seasonal thermoregulatory costs of resting in the two microsites. Although pygmy rabbits demonstrated seasonal physiological acclimatization, the burrow was an important thermal refuge, especially in winter. Thermoregulatory costs were lower inside the burrow than in above-ground rest sites for more than 50% of the winter season. In contrast, thermal heterogeneity provided by above-ground rest sites during summer reduced the role of burrows as a thermal refuge during all but the hottest periods of the afternoon. Our findings contribute to an understanding of the ecology of small mammals in seasonal environments and demonstrate the importance of burrows as thermal refuge for pygmy rabbits.
在热环境具有强烈季节变化的栖息地中，小型哺乳动物通常会表现出生理和行为上的适应性，以应对极端温度并降低体温调节成本。当地面温度需要高昂的调节成本（如水或能量）或超过生物体的生理耐受范围时，洞穴对于提供热避难所尤为重要。我们的目标是通过量化与在地面以上和以下休息相关的能量成本，来探究洞穴在夏季和冬季作为小型恒温动物侏兔的热避难所的作用。我们使用间接量热法来确定在侏兔自然栖息地所经历的一系列温度范围内，能量消耗与环境温度之间的关系。我们还测量了美国爱达荷州东部侏兔在夏季和冬季使用的地面以上和以下休息地点的温度，并估算了在这两个微生境中休息的季节性体温调节成本。尽管侏兔表现出季节性生理适应，但洞穴是一个重要的热避难所，尤其是在冬季。在超过50%的冬季时间里，洞穴内的体温调节成本低于地面以上的休息地点。相比之下，夏季地面以上休息地点提供的热异质性降低了洞穴在除下午最热时段之外的所有时间作为热避难所的作用。我们的研究结果有助于理解季节性环境中小型哺乳动物的生态学，并证明洞穴作为侏兔热避难所的重要性。
