Seasonal variations in locomotor activity rhythm and diurnal activity in the dromedary camel (Camelus dromedarius) under mesic semi-natural conditions

ABSTRACT

The dromedary camel (Camelus dromedarius) 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.

KEYWORDS:

• Camel
• locomotor activity rhythm
• seasonal changes
• diurnality
• temporal niche switching
• daily ambient temperature cycle
• light intensity

Acknowledgements

The authors are grateful to Hassan II Agronomy and Veterinary Medicine Institute (Rabat, Morocco) and the Institute of Cellular and Integrative Neurosciences (CNRS and University of Strasbourg, France) for supporting this study.

Disclosure statement

The authors declare no competing interests.

Author contributions

HF Performed the experiments; Analyzed and interpreted the data and drafted the manuscript. DH Performed the experiments; Analyzed and interpreted the data. MRA. Analyzed and interpreted the data and drafted the manuscript. MP; MO and BB. Contributed reagents, materials, analysis tools or data and drafted the manuscript. PP and EC. Conceived and designed the experiments; Analyzed and interpreted the data and drafted the manuscript. KE. Conceived and designed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data and drafted the manuscript.

Additional information

Funding

This work was supported by the Hassan II Institute of Agronomy and Veterinary Medicine of Rabat-Morocco and the International Foundation for Science [IFS: Research Grant Agreement N°: I-3-B-6082-1].