Shiratsuru Shotaro, Friebe Andrea, Swenson Jon E, Zedrosser Andreas
Department of Biological Sciences University of Alberta Edmonton AB Canada.
Scandinavian Brown Bear Research Project Orsa Sweden.
Ecol Evol. 2020 Jul 20;10(15):8044-8054. doi: 10.1002/ece3.6371. eCollection 2020 Aug.
Hibernation is an adaptive strategy to survive harsh winter conditions and food shortage. The use of well-insulated winter dens helps animals minimize energy loss during hibernation. Brown bears () commonly use excavated dens for hibernation. Physical attributes of excavated dens are expected to impact the bear's heat retention and energy conservation. The objective of this study was to examine the determinants of cavity size of excavated dens and the impact of physical attributes of excavated dens on energy conservation in hibernating bears, hypothesizing that bears excavate dens in a way to minimize heat loss and optimize energy conservation during hibernation. We predicted that den cavity size would be determined by the bear's body size and that older bears would excavate better-fitting cavities to minimize heat loss, due to their previous experience. We further predicted that physical attributes of excavated dens would affect the bears' posthibernation body condition. Our results revealed that bears excavated a den cavity in relation to their body size, regardless of sex, and that older bears tended to excavate better-fitting den cavities compared to young bears, as we expected. Older bears excavated better-fitting den cavities, suggesting a potentially experience-based shift with age in den-excavation behavior and an optimum cavity size relative to a bear's body size. Our key finding is that insulation of excavated dens provided by wall/rood thickness and bedding materials had a significant positive effect on bears' posthibernation body condition. We believe that our study provides new insight into how not only the quality of denning habitat, but also the quality of dens may affect hibernating animals, by presenting a potential adaptive aspect of den preparation (age effect on efficiency in den excavation) and effect of den attributes on the posthibernation body condition of brown bears.
冬眠是一种适应策略，用于在严酷的冬季条件和食物短缺的情况下生存。使用保温良好的冬季洞穴有助于动物在冬眠期间将能量损失降至最低。棕熊通常使用挖掘出的洞穴进行冬眠。挖掘出的洞穴的物理属性预计会影响熊的热量保持和能量保存。本研究的目的是研究挖掘出的洞穴的腔室大小的决定因素以及挖掘出的洞穴的物理属性对冬眠熊能量保存的影响，假设熊挖掘洞穴的方式是为了在冬眠期间将热量损失降至最低并优化能量保存。我们预测洞穴腔室大小将由熊的体型决定，并且由于年长的熊有先前的经验，它们会挖掘出更合适的腔室以将热量损失降至最低。我们进一步预测挖掘出的洞穴的物理属性会影响熊冬眠后的身体状况。我们的结果表明，无论性别如何，熊都会根据自己的体型挖掘洞穴腔室，并且正如我们所预期的，年长的熊与年轻的熊相比，往往会挖掘出更合适的洞穴腔室。年长的熊挖掘出更合适的洞穴腔室，这表明随着年龄增长，洞穴挖掘行为可能基于经验发生转变，并且相对于熊的体型存在一个最佳腔室大小。我们的关键发现是，由墙壁/屋顶厚度和铺垫材料提供的挖掘出的洞穴的隔热对熊冬眠后的身体状况有显著的积极影响。我们相信，我们的研究通过展示洞穴准备的一个潜在适应性方面（年龄对洞穴挖掘效率的影响）以及洞穴属性对棕熊冬眠后身体状况的影响，为不仅洞穴栖息地的质量，而且洞穴的质量如何影响冬眠动物提供了新的见解。
