Locomotor activity patterns of laboratory mice are widely used to analyze circadian mechanisms, but most investigations have been performed under standardized laboratory conditions. Outdoors, animals are exposed to daily changes in photoperiod and other abiotic cues that might influence their circadian system. To investigate how the locomotor activity patterns under outdoor conditions compare to controlled laboratory conditions, we placed 2 laboratory mouse strains (melatonin-deficient C57Bl and melatonin-proficient C3H) in the garden of the Dr. Senckenbergische Anatomie in Frankfurt am Main. The mice were kept singly in cages equipped with an infrared locomotion detector, a hiding box, nesting material, and with food and water ad libitum. The locomotor activity of each mouse was recorded for 1 year, together with data on ambient temperature, light, and humidity. Chronotype, chronotype stability, total daily activity, duration of the activity period, and daily diurnality indices were determined from the actograms. C3H mice showed clear seasonal differences in the chronotype, its stability, the total daily activity, and the duration of the activity period. These pronounced seasonal differences were not observed in the C57Bl. In both strains, the onset of the main activity period was mainly determined by the evening dusk, whereas the offset was influenced by the ambient temperature. The actograms did not reveal infra-, ultradian, or lunar rhythms or a weekday/weekend pattern. Under outdoor conditions, the 2 strains retained their nocturnal locomotor identity as observed in the laboratory. Our results indicate that the chronotype displays a seasonal plasticity that may depend on the melatoninergic system. Photoperiod and ambient temperature are the most potent abiotic entraining cues. The timing of the evening dusk mainly affects the onset of the activity period; the ambient temperature during this period influences the latter's duration. Humidity, overall light intensities, and human activities do not affect the locomotor behavior.

中文翻译：

---

在半自然的户外条件下，能褪黑激素的和缺乏的小鼠的运动活动节律的季节性变化。

实验室小鼠的运动活动模式已广泛用于分析昼夜节律机制，但大多数研究已在标准化实验室条件下进行。在户外，动物会遭受光周期和其他非生物信号的日常变化，这可能会影响其昼夜节律系统。为了研究室外条件下的运动活动模式与受控实验室条件下的运动模式之间的关系，我们在美因河畔法兰克福的Senckenbergische Anatomie博士的花园中放置了2种实验室小鼠品系（褪黑激素缺陷型C57B1和褪黑激素敏感型C3H）。将小鼠单独饲养在装有红外运动检测器，藏身箱，筑巢材料以及任意食物和水的笼子中。记录每只小鼠的运动活动1年，以及有关环境温度的数据，光线和湿度。从活动图上确定了计时型，计时型稳定性，每日总活动量，活动时间长短和每日昼夜指数。C3H小鼠在表型，稳定性，每日总活动量和活动持续时间方面表现出明显的季节性差异。在C57B1中未观察到这些明显的季节性差异。在这两个菌株中，主要活动期的开始主要由傍晚黄昏决定，而偏移量则受环境温度的影响。动作图未显示出下，节律或月球节律或工作日/周末模式。在室外条件下，这两种菌株保留了在实验室中观察到的夜间运动特性。我们的结果表明，该表型显示出季节性可塑性，这可能取决于褪黑素能系统。光周期和环境温度是最有效的非生物夹带线索。傍晚黄昏的时间主要影响活动时间的开始。在此期间的环境温度会影响环境温度的持续时间。湿度，整体光照强度和人类活动不会影响运动行为。