Differences between fast and slow explorers in short-term tail temperature responses to handling in a rodent of wild origin.

Animals of different behavioral types typically show associated differences in their physiological stress response, including differential reactivity of the sympathetic nervous system. Infrared thermography offers the possibility to explore this link in a non-invasive way via the quantification of fine-scale changes in peripheral body temperature due to changes in cutaneous blood flow. We used this technique to investigate the association between exploration tendency, a behavioral trait frequently used to phenotype mammals and birds, and short-term thermal responses to challenge in a small rodent of wild origin, the mound-building mouse (Mus spicilegus). We applied a brief handling procedure consisting in the transfer of subjects into a small arena. This procedure led to a significant increase in subjects' maximum peripheral body temperature (mainly reflecting the temperature of the eyes) and to significant decreases in maximum temperatures at different positions on the tail. Maximum peripheral body and tail temperatures showed significant individual-level consistencies in response to repeated applications of the handling procedure, suggesting stable individual differences in the animals' sympathetic activity. We then compared the thermal responses to handling between 'fast' and 'slow' explorers, who were phenotyped through repeated open field and novel object tests. Fast explorers showed significantly lower tail temperatures than slow explorers shortly after handling, suggesting a stronger sympathetic reactivity in the former. Comparisons within sibling groups kept in different cages showed that the differences between explorer types were particularly pronounced during the first minute after handling, and increased in magnitude along the first millimeters distal to the tail base.