Development of Insulation in Neonatal Cotton Rats (Sigmodon hispidus)

Abstract

Data on environmental temperatures, skin temperature, animal size, the depth of fur, density of hairs in fur, hair length, and diameter of hair shafts were used to calculate fur thermal conductivity and heat loss, using a porous medium model modified from that of Kowalski and Mitchell. The total thermal conductivity of fur changed little with respect to the age of the animal, but calculated heat loss per unit area decreased because of a decrease in the thermal gradient across the fur caused by an increase in fur depth. A sensitivity analysis of the model showed that skin, air, and radiant environmental temperatures were most important in determining heat loss in all sizes of animals. Fur depth is the only important property of fur determining heat loss in nestling rats, but in adults, all the properties of fur exert significant effects on heat loss. The diameter of animals is a significant variable in all sizes of rats.