Hair corticosterone and cortisol concentrations during laboratory housing in wild-caught arvicoline and murine...

Hair glucocorticoid concentrations are increasingly used as proxies of longer-term glucocorticoid exposure in wild and laboratory animals. In this study, we measured hair corticosterone concentrations in the common vole Microtus arvalis (Arvicolinae) and the striped field mouse Apodemus agrarius (Murinae) to assess: (1) changes associated with three months of laboratory housing in adults; (2) age-related variation between adult voles and 15-day-old juveniles; and (3) sex-related differences in hair corticosterone concentrations. Hair cortisol was also quantified as a complementary and exploratory measure to determine whether it showed a pattern comparable to corticosterone across species and sampling time points. Hair samples were collected from wild-caught adults three days after capture, before the three-month experimental period, and again after three months of laboratory housing. Hair from juvenile voles was collected on postnatal day 15. Corticosterone and cortisol concentrations were quantified using two commercial ELISA kits. Hair corticosterone concentrations increased markedly in M. arvalis during laboratory housing, whereas in A. agrarius the increase was restricted to females. Fifteen-day-old juveniles showed significantly lower hair corticosterone concentrations than adults. An exploratory analysis did not detect an association between maternal and offspring hair corticosterone concentrations, but this analysis was limited by the small number of mothers. Hair cortisol concentrations remained low and showed no statistically detectable changes between sampling time points. These findings indicate that hair glucocorticoid measurements may provide information on longer-term glucocorticoid exposure in small mammals, while emphasising that their interpretation requires consideration of species, developmental stage, sex, housing history and analytical limitations.