Wintertime loss of ultradian and circadian rhythms of body temperature in the subterranean euthermic mole vole, ellobius talpinus.

Subterranean common mole voles, Ellobius talpinus, were implanted with long-term recording electronic thermometers to obtain hourly body temperature (T(b)) data during either the wintertime or summertime. The two individuals tested during the summertime had significant circadian and ultradian rhythms in their T(b). Four of the five mole voles tested during the wintertime lacked rhythmicity in their T(b). The fifth individual lacked circadian rhythms but had ultradian rhythms in its T(b). A loss of circadian rhythms in T(b) during deep torpor or hibernation has been reported for a few species of mammals. Inasmuch as the mole voles' wintertime T(b) remained at euthermic levels, our results show that a loss of circadian body temperature rhythms in mole voles does not require the low T(b) of deep torpor or hibernation. A tentative conclusion, based on these few animals, is that in common mole voles the T(b) rhythms may disappear during the wintertime even though their T(b) remains high.