Tail skin temperatures reflect coping styles in rats.

This study was carried out to elucidate the predictive value of tail skin temperatures (TSTs) assessed in naïve rats as a non-invasive pre-experimental method of classification of coping style. Male Lewis rats were classified according to tail skin temperatures (TST), and relative size within cage-groups. TSTs were monitored over two-hour periods following exposure to physical and emotional stressors. Bodyweight-shifts associated to the experiments were analysed. Six organs of neuroendocrine relevance to allostasis were weighed. Challenge-specific TST-profiles were size-related and consistent with proactive or reactive coping. Pro-active (A) rats showed a more pronounced TST-response to unknown conspecifics, but reactive (B) rats to environmental novelties. B-rats showed challenge-specific weight-losses while A-rats gained more after experiments. Second size males showed rapidly decreased TSTs (vasoconstriction) after nociceptive stimulation. Males that showed the highest basal TSTs and weight-loss in emotionality tests had lost a first rank position during a pre-experimental period, suggesting long-lasting effects of social defeat. Pre-experimental growth correlated positively to adiposisity post-experimentally, but negatively to testes relative weight in B-rats. Scaling effects explained heart-size in B-rats and pituitary-size in A-rats. The overall patterns that emerged, in factor analyses including organ sizes, were consistent with pro-active coping in A-rats and reactive in B-rats. Our results, controlling for rank-effects, suggest that non-invasively assessed TSTs may predict individual stress-coping phenotypes pre-experimentally in rats housed in groups.