Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature (T_a), has received much less attention. To address this dearth of knowledge, we exposed two subterranean endothermic-homeothermic African mole-rat species, the solitary Cape mole-rat (Georychus capensis [GC]) and social Mahali mole-rat (Cryptomys hottentotus mahali [CHM]), to varying T_a cycles in the absence of light. We showed that the LA rhythms of these two species entrain to T_a cycles and that the majority of LA occurred during the coolest 12-h period. LA confined to the coolest T_a periods may be the direct consequence of the poor heat dissipation abilities of African mole-rats brought about by physiological and ecological constraints. Recently, it has been hypothesized that T_a is only a strong zeitgeber for circadian rhythms in species whose thermoregulatory abilities are sensitive to changes in T_a (i.e., heterotherms and ectotherms), which previously has excluded endothermic-homeothermic mammals. However, this study demonstrates that T_a is a strong zeitgeber or entrainer for circadian rhythms of LA in subterranean endothermic-homeothermic mammals as a consequence of their sensitivity to changes in T_a brought about by their poor heat dissipation abilities. This study reinforces the intimate link between circadian rhythms and thermoregulation and conclusively, for the first time, provides evidence that T_a is a strong zeitgeber for endothermic-homeothermic mammals.

哺乳动物在内部生物过程和行为（例如运动活动 (LA)）中进化出了昼夜节律，以与它们所经历的环境条件同步。LA 的光夹带已经很成熟；然而，非光夹带，例如环境温度 ( T _a )，却很少受到关注。为了解决这种知识的缺乏，我们将两种地下吸热-恒温非洲鼹鼠物种，即独居的海角鼹鼠（Georychus capensis [GC]）和群居鼹鼠（Cryptomys hottentotus mahali [CHM]）暴露于不同的环境中。T _a在没有光的情况下循环。我们表明这两个物种的 LA 节律夹带到T _a循环并且大部分 LA 发生在最冷的 12 小时期间。LA 被限制在最冷的T _a时期可能是非洲鼹鼠受生理和生态限制导致散热能力差的直接后果。最近，有人假设，对于体温调节能力对T _{a 的}变化（即异温和变温）变化敏感的物种，T _a只是昼夜节律的强时间段，此前已将吸热-恒温哺乳动物排除在外。然而，这项研究表明，T _a是一个强大的时代或夹带地底吸热恒温哺乳动物 LA 昼夜节律，因为它们对散热能力差引起的T _a变化很敏感。这项研究加强了昼夜节律和体温调节之间的密切联系，并最终首次提供了证据，证明T _a是吸热-恒温哺乳动物的强大时代。