Metabolism and thermal response in winter-acclimatized pygmy rabbits (Brachylagus idahoensis)

Abstract

Resting metabolic rate of pygmy rabbits (0.89 ml O2 g-1 h-1) was high compared to other eutherian mammals, but not unusual among lagomorphs. The estimated size of the zone of thermoneutrality was ca. 8-9°C, with the lower critical temperature occurring between 15 and 2O°C, depending on body mass. Minimum thermal conductance was lower and mean body temperature was higher than predicted for similarly sized mammals. Body temperature fluctuated >1°C within a 24-h period, but showed no circadian patterns. Pygmy rabbits are thermally stressed during harsh winters in Wyoming, but low thermal conductance, a highenergy source of food, and favorable microenvironments enhance survival.