Small mammals that are specialists in homeothermic thermoregulation reduce their self-maintenance costs of normothermy to survive the winter. By contrast, heterothermic ones that are considered generalists in thermoregulation can lower energy expenditure by entering torpor. It is well known that different species vary the use of their strategies to cope with harsh winters in temperate zones; however, little is still known about the intraspecific variation within populations and the associated external and internal factors. We hypothesized that yellow-necked mice Apodemus flavicollis decrease their resting metabolic rate (RMR) from autumn to winter, and then increase it during spring. However, since the alternative for seasonal reduction of RMR could be the development of heterothermy, we also considered the use of this strategy. We measured body mass (m_b), RMR, and body temperature (T_b) of mice during two consecutive years. In the first year, mice decreased whole animal RMR in winter, but did not do so in the second year. All mice entered torpor during the second winter, whereas only a few did so during the first one. Mice showed a continuous increase of m_b, which was steepest during the second year. The relationship between RMR and m_b varied among seasons and years most likely due to different mouse development stages. The m_b gain at the individual level was correlated positively with RMR and heterothermy. This indicates that high metabolism in winter supports the growth of smaller animals, which use torpor as a compensatory mechanism. Isotope composition of mice hair suggests that in the first year they fed mainly on seeds, while in the second, they likely consumed significant amounts of less digestible herbs. The study suggests that the use of specialist or generalist thermoregulatory strategies can differ with environmental variation and associated differences in developmental processes.

中文翻译：

---

冬季持续生长与静息代谢率增加有关，但不因使用玉米粥而影响每日能量预算

专门从事恒温疗法的小型哺乳动物降低了其常温维持冬季的自我维护成本。相比之下，被认为是温度调节方面通才的异热反应堆可以通过进入entering孔来降低能量消耗。众所周知，不同的物种会改变其策略的使用方式，以应对温带地区的严冬。然而，关于种群内种内变异以及相关的外部和内部因素，仍然知之甚少。我们假设黄颈小鼠淡淡姬鼠从秋季到冬季降低他们的静息代谢率（RMR），然后在春季增加。但是，由于替代RMR季节性降低的方法可能是开发异温热，因此我们也考虑了使用该策略。我们在连续两年中测量了小鼠的体重（m _b），RMR和体温（T _b）。在第一年，小鼠在冬季降低了整个动物的RMR，但在第二年没有这样做。在第二个冬季，所有小鼠进入了torpor，而在第一个冬季中，只有少数小鼠进入了。小鼠显示m _b连续增加，第二年最陡。RMR和m _b之间的关系季节和年份之间的差异很大，这很可能是由于小鼠的发育阶段不同所致。所述米_b在个体水平增益用RMR和heterothermy正相关。这表明冬季较高的新陈代谢支持较小的动物的生长，这些动物使用玉米粥作为补偿机制。小鼠头发的同位素组成表明，第一年它们主要以种子为食，而第二年中，它们可能会食用大量不易消化的草药。该研究表明，专业或通用温度调节策略的使用可能随环境变化和发展过程中的相关差异而有所不同。