A preliminary study on the seasonal body temperature rhythms of the captive mountain hare (Lepus timidus)

The mountain hare (Lepus timidus) is a year-round active herbivore adapted to survive the boreal winter. Captive mountain hares (N = 4) were implanted with intraabdominal thermosensitive loggers to record their core body temperature (Tb) for a year and during food deprivation (8–48 h) in summer and winter. The average Tb was 38.7 ± 0.01 °C in summer and 38.3 ± 0.01 °C in winter. The yearly Tb correlated positively with the ambient temperature. The 24-h Tb was the highest from late scotophase to early photophase in summer and winter and the lowest during middle-late photophase in summer or during early-middle scotophase in winter. The range of the 24-h oscillations in Tb increased in three animals in winter. Food deprivation did not induce hypothermia in summer or winter. These preliminary data suggest that the mountain hare can spare a modest amount of energy with the wintertime reduction in Tb.