A newly discovered behavior ('tail-belting') among wild rodents in sub zero conditions

Rodents are among the most successful mammals because they have the ability to adapt to a broad range of environmental conditions. Here, we present the first record of a previously unknown thermal adaptation to cold stress that repeatedly occurred in two species of non-commensal rodents (Apodemus flavicollis and Apodemus agrarius). The classic rodent literature implies that rodents prevent heat loss via a broad range of behavioral adaptations including sheltering, sitting on their tails, curling into a ball, or huddling with conspecifics. Here, we have repeatedly observed an undescribed behavior which we refer to as "tail-belting". This behavior was performed under cold stress, whereby animals lift and curl the tail medially, before resting it on the dorsal, medial rump while feeding or resting. We documented 115 instances of the tail-belting behavior; 38 in Apodemus agrarius, and 77 in Apodemus flavicollis. Thermal imaging data show the tails remained near ambient temperature even when temperatures were below 0 °C. Since the tail-belting occurred only when the temperature dropped below - 6.9 °C (for A. flavicollis) and - 9.5 °C (for A. agrarius), we surmise that frostbite prevention may be the primary reason for this adaptation. It is likely that tail-belting has not previously been documented because free-ranging mice are rarely-recorded in the wild under extreme cold conditions. Given that these animals are so closely-related to laboratory rodents, this knowledge could potentially be relevant to researchers in various disciplines. We conclude by setting several directions for future research in this area.