Seasonal and diurnal variability of the body temperature in the northern white-breasted hedgehog (Erinaceus roumanicus) in normothermia
Both during hibernation at normothermia and while the animals are active in summer the body temperature of hedgehogs fluctuates significantly in the range from 26 to 38°C. Seasonal variability in body temperature is related to reproduction and ambient temperature. During the breeding season in May and June, the body temperature of hedgehogs is significantly higher in both males and females comparing to other seasons. This is probably due to the period of active reproduction and seasonal variability in the hormones’ content in blood. The average daily body temperature in hedgehogs correlates with the ambient temperature in the summer months - May and June, when the night air temperatures do not differ much from those during daytime one and are of the optimal range for hedgehogs. In spring, at the end of summer, and in autumn, the ambient temperature may drop significantly, being out of the optimal range, and the animal body temperature does not always follow the ambient temperature changes, so no reliable correlation between them are observed. The body temperature of hedgehogs during the day is not constant: during the daytime rest in summer period, most hedgehogs have a lower body temperature, which probably saves energy. During the non-hibernation period, females usually have a higher body temperature comparing to males, which may be associated with physiological features and, in particular, with a higher metabolism. The photoperiod affects the duration of activity of hedgehogs and, accordingly, the time during which the body temperature of hedgehogs is elevated at night. During normothermia at the hibernation period, ultradian rhythms are observed for the animal body temperature with periods of 4.0-4.3 h; apparently, they are masked by the influence of other factors during the period of activity of hedgehogs.