Seasonal activity in the blind mole rat (Spalax ehrenbergi)

Abstract

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.

Melatonin secretion in a strictly subterranean mammal, the Damaraland mole‐rat (Cryptomys damarensis)

“…The absence of light underground suggests that subterranean mammals are normally deprived of the most ubiquitous zeitgeber to time life-history events, namely photoperiod. However, it has been suggested that brief exposure to light can entrain melatonin secretion in subterranean rodents (Rado et al, 1993;Reiter, Reiter et al, 1994), as it does in some other species (Reiter, 1993;Shanahan et al, 1997). In this study, melatonin secretion in a strictly subterranean rodent C. damarensis was found to be both diurnal and circadian, but relatively insensitive to acute exposure to light and dark.…”

Animal activity around the clock with no overt circadian rhythms: patterns, mechanisms and adaptive value

“…Both solitary and social mole rats typically show clear circadian rhythms and entrainment when monitored individually in the laboratory, indicating that they have a functional circadian clock [37][38][39]. Telemetry studies suggest that solitary mole-rats also show circadian rhythms under natural field conditions [39,40]. By contrast, eusocial naked mole-rats Heterocephalus gIaber and Damaraland mole-rats (Fukomys damarensis) show attenuated or no circadian rhythms, and are active around the clock when monitored in the social context of the colony [37,41,42].…”

Distinguishing bioturbation and trampling using pottery sherd measures, Tell Fendi, Jordan

“…Zoologists have studied mole-rat behavior extensively, and several of these studies are of particular interest to geoarchaeologists (e.g., Nevo, 1961;Bruder, 1982;Heth, 1989;Rado et al, 1993;Zuri and Terkel, 1996). Heth (1989) excavated 19 mole-rat tunnels in the Mount Carmel region of Israel and plotted their size, direction, and depth to determine if activities differed by soil type.…”