Circadian body temperature rhythms of the solitary cape mole rat Georychus capensis (Bathyergidae).

Simultaneous measurements of activity and telemeterized body temperature were measured under 12:12 LD and constant light conditions in the solitary, subterranean rodent Georychus capensis for 137 consecutive days. The objectives of the study were twofold: a) to determine whether G. capensis display circadian body temperature rhythms similar to those of nonsubterranean mammals, and b) to determine whether body temperature rhythms provide a more reliable measure than those of activity of endogenous circadian rhythms under laboratory conditions. Significant circadian Tb and activity rhythms were recorded under entrained and free-running conditions (i.e., under a light-dark cycle and under constant illumination), confirming the ability of this species to perceive light. Although the maximum daily amplitude of Tb (Rt) between the mean photophase minimum and the mean scotophase maximum was 99% of that predicted by body mass for mammals, G. capensis did not display sustained differences of either the minimum, mean, or maximum Tb between the photo- and scotophases. Nevertheless, most individuals indicated nocturnal activity patterns. Evidence suggests a lack of an obvious endogenous body temperature rhythm. Body temperature may thus not be a reliable measure of endogenous circadian rhythms in this rodent.