Seasonal activity in the blind mole rat (Spalax ehrenbergi)

The locomotor activity pattern of the blind mole rat Spalax ehrenbergi was determined in its natural habitat by means of a radiotelemetric device. Twelve adult mole rats were fitted with radiotelemetric transmitters (9 during winter and 3 during summer) and tracked for 5 noncontinuous days during which air and soil temperatures were measured. Mole rats were found to have a diurnal monophasic locomotor activity pattern with activity peaks from 08:00 to 13:00 and from 11:00 to 19:00 during summer and winter, respectively. Activity periods were punctuated by several rest breaks and, conversely, rest periods were interrupted by short spells of activity. Duration of activity was 6.6 ± 0.4 h (mean ± SD) in summer and 7.9 ± 2.3 h in winter. In the laboratory, mole rats were found to entrain their activity, under constant dim light, to a single daily 20-s light pulse. Moreover, such a light pulse given only once every 3 days was found to provide a stimulus sufficient to entrain the mole rats' locomotor activity. We propose that brief light pulses perceived through the mole rats' rudimentary eyes while they are pushing excess soil out of the tunnel to the ground surface, are the main Zeitgeber that entrains their locomotor activity to the diurnal pattern. Air and soil temperatures are the secondary cues that finely tune the activity to the morning during summer and the late afternoon during winter.