Body temperature changes in wild‐living badgers Meles meles through the winter

In central Norway, the body temperatures of two wild‐living badgers Meles meles , one male and one female, were recorded in the morning and evening from early November to late March using an implanted temperature‐sensitive radio transmitter. The external ambient and internal sett temperatures were also recorded. Both badgers showed a general decrease in their mean daily body temperature from early November until the second half of December, followed by a general increase until the beginning of March. The reduction in body temperature for both animals was around 2–3 °C. The female spent most of the winter under a building, in a crawl space where the internal temperature varied from +4°C to ‐11°C, being strongly influenced by the external ambient temperature. The male spent the winter in a natural sett where the temperature was rather constant (+2–5°C), and where the external ambient temperature had little influence on the internal sett temperature. However, the external ambient temperature only accounted for 11 and 12% of the observed body temperature variations in the male and female, respectively. When the length of daylight was compared with the body temperatures, it was found to account for 60 and 30% of the variations in the male and female temperatures, respectively. Thus, the data indicate that the photoperiod, at its minimum at the winter solstice, acted as the primary synchroniser of the body temperature cycle in the badgers during their winter lethargy.