Fat Deposition and Seasonal Variation in Body Composition of Arctic Foxes in Svalbard

We studied the seasonal variation in body composition of arctic foxes (Alopex lagopus) to determine the adaptive significance of fat deposition in this species. Homogenates of 75 minced fox carcasses were analyzed. On a large sample of animals trapped in 1982-89, the thickness of subcutaneous fat was measured, and the amount of fat was indexed subjectively. Fat was deposited both subcutaneously and viscerally in September-October, and it reached a maximum of about 20% of the skinned carcass mass in November. The amount of fat deposited did not decline between November and March of any year. The fat deposits were depleted from March through May, reaching about 6% of the carcass mass by the summer. Fifteen percent of the trapped foxes did not have any subcutaneous or visceral fat deposits in winter