THERMOREGULATION
The normal body temperature is 38.5-39.5° C (Brewer & Cruise 1994). Rabbits are extremely sensitive to heat so should be housed at between 15 and 21° C (Batchelor 1999). They cannot sweat and have an inefficient salivation and panting mechanism.
In the wild, they cool down by seeking shade in their burrows or stretching out to increase body surface area. The long ears are also essential for heat dispersion, having a countercurrent arteriovenous shunt. In fact, directly cooling the ears causes a drop in body core temperature and vice versa (Brewer & Cruise 1994; Cheeke 1987c).High temperatures also inhibit drinking and panting, which can hasten dehydration and be fatal. Rabbits are also sensitive to low humidity but, as underground burrows are naturally quite humid, high humidity levels are not a problem.
Unlike rodents, adult rabbits possess no brown fat and so they shiver when cold and retain body heat by shunting warm blood from the ears to warm the body core. They also adopt a hunched posture and huddle together to decrease the collective surface area (Cheeke 1987c).