Adaptation of the red fox (Vulpes vulpes) body weight and thickness of the limbs to snow conditions in Scandinavia
Intraspecific variation in body weight is a common phenomenon in many mammals and is largely related to variation in quality and abundance of foods. The amount of food in the spring–summer period may affect the growth of the young animals and in winter time affect the fat reserves both affecting the body weight. In this study I examined the winter body weight in adult red foxes Vulpes vulpes in five areas in Scandinavia. The amount of food varied strongly between years in the three northern areas. The winter body weight also varied between years, but this was not a result of that foxes in years with plenty of food were fatter. The reason was differences between years in the proportion of foxes born in years with varying amount of voles. Foxes in the north down to the central part of Sweden are of the same size at least the phenotypes. In spite of that foxes are heavier southwards. The reason is that foxes in the north have thinner bones, probably an adaptation to the amount of snow. In Scania in the most southern part of Sweden the foxes are the largest in Scandinavia and therefore the heaviest. Danish foxes are not as heavy as foxes in Scania. When studying the weights of wild animals in areas where food sometimes is extremely scarce, such as near the limits of the species range, it is important to treat data from different birth cohorts separately. To ignore that may result in misleading conclusions.DOI: 10.15298/rusjtheriol.19.1.07
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