Comparison of Microstructure of White Winter Fur and Brown Summer Fur of Some Arctic Mammals

Several species of Arctic mammals have brown hair in the summer and molt into a white pelage in the winter. It is unknown whether characteristics other than color of the hair also change during the color transition between seasons. We borrowed guard hair samples from museums to represent summer and winter pelages of five species: Alopex lagopus (Arctic fox), Lepus americanus (snowshoe hare), Lepus Arcticus (Arctic hare), Mustela erminea (ermine) and Mustela nivalis (least weasel). Micro‐structural differences exist between the brown and white hairs. In general, white winter hairs had larger upper shaft medullas comprising more air‐filled cells and smaller lower shafts. These structural changes may function in conservation of heat or in increasing light reflection to whiten the fur and aid as camouflage.