Circadian and ultradian rhythms in free living bank voles (Myodes glareolus)
Abstract: Data of 17,065 recordings in baited camera traps in the Netherlands revealed that bank voles (Myodes glareolus) expressed most activity between sunset and sunrise, with an exception for June-July. When corrected for the duration of respectively night and day the nocturnal bias was observed in all months, but was stronger when nights were longer. On top of the circadian rhythm, a rather distinct ultradian rhythm was superimposed, especially during the night. Activity peaked just after sunset in August-March, during sunset in April-May and before sunset in June-July, to be followed by a series of 1-4 distinct peaks and lows during the night. For full cycles (from peak to peak or low to low), mean duration was 224 minutes. Activity was highly synchronised between traps (individuals), areas separated by unsuitable habitat (populations) and years.