cComparative Anatomy Unit, Department of Biological and Pharmacological Veterinary Sciences, Hassan IInd Agronomy and Veterinary Medicine Institute, Rabat, Morocco.
Medicine and Surgical Unit of Domestic Animals, Department of Medicine, Surgery and Reproduction, Hassan IInd Agronomy and Veterinary Medicine Institute, Rabat, Morocco.
Chronobiol Int. 2022 Jan;39(1):129-150. doi: 10.1080/07420528.2021.1984936. Epub 2021 Dec 29.
The dromedary camel () is a large ungulate that copes well with the xeric environment of the desert. Its peculiar adaptation to heat and dehydration is well-known. However, its behavior and general activity is far from being completely understood. The present study was carried out to investigate the ecological effect of the various seasons on the locomotor activity (LA) rhythm and diurnal activity of this species. Six adult female camels were maintained under mesic semi-natural conditions of the environment during four periods of 10 days in each season: autumn, winter, spring and summer. In addition, three female camels were used to test the effect of rain on the LA rhythm during a period of 18 days during the winter. The animal's LA was recorded using the locomotion scoring method. Camels displayed a clear 24.0h LA rhythm throughout the four seasons. Activity was intense during Day-time (6-22 fold higher in comparison to night) and dropped or completely disappeared during nighttime. Mean daytime total activity was significantly higher in the summer as compared to winter. Regardless of the season, the active phase in camels coincided with the time of the photophase and thermophase. Furthermore, the daily duration of the time spent active was directly correlated to the seasonal changes of photoperiod. The diurnal activity remained unchanged over the four seasons. For each season, the start and the end of the active phase were synchronized with the onset of sunrise and sunset. At these time periods, temperature remained incredibly stable with a change ranging from 0.002 to 0.210°C; whereas, changes of light intensity were greater and faster with a change from 0.1 to 600 lux representing a variation of 3215-7192 fold in just 25-29 min. Rainfall affected the pattern of the LA rhythm with occurrence of abnormal nocturnal activity during nighttime disturbing nocturnal rest and sleep. Here we show that the dromedary camel exhibits significant seasonal changes of its activity within daylight hours. However, the diurnal pattern remains unchanged regardless of the season; whereas, abnormal nocturnal activity is observed during periods of rain. The activity onset and offset in this species seems to be primarily driven by the changes in light intensity at dusk and dawn.
单峰驼（）是一种大型有蹄动物，能很好地适应沙漠的干旱环境。它对热和脱水的特殊适应能力是众所周知的。然而，它的行为和一般活动远未被完全理解。本研究旨在调查不同季节对该物种运动活动（）节律和日间活动的生态影响。六只成年雌性骆驼在四个季节的 10 天内分别维持在湿润半自然环境条件下：秋季、冬季、春季和夏季。此外，三只雌性骆驼在冬季的 18 天内用于测试雨对的影响。动物的通过运动评分法记录。骆驼在四个季节都表现出明显的 24.0h 节律。白天活动强度较高（比夜间高 6-22 倍），夜间活动减弱或完全消失。与冬季相比，夏季白天总活动量明显较高。无论季节如何，骆驼的活跃期都与光相和热相吻合。此外，每日活动时间的长短与光周期的季节性变化直接相关。四个季节的昼夜活动保持不变。对于每个季节，活跃期的开始和结束与日出和日落的开始同步。在这些时间段，温度保持惊人的稳定，变化范围从 0.002 到 0.210°C；而光照强度的变化更大更快，从 0.1 到 600 勒克斯变化，在 25-29 分钟内变化 3215-7192 倍。降雨影响了的节律模式，夜间出现异常的夜间活动，扰乱了夜间休息和睡眠。在这里，我们表明，单峰驼在白天的活动表现出显著的季节性变化。然而，无论季节如何，昼夜模式保持不变；然而，在降雨期间会观察到异常的夜间活动。该物种的活动开始和结束似乎主要由黄昏和黎明时光照强度的变化驱动。
