Dahle, B., Sørensen, O.J., Wedul, E.H., Swenson, J.E. & Sandegren, F. 1998: The diet of brown bears Ursus arctos in central Scandinavia: effect of access to free-ranging domestic sheep Ovis aries. - Wildl. Biol. 4: 147-158.
The seasonal food habits of brown bears Ursus arctos were estimated based on the analysis of 266 scats in central Norway and Sweden. Free-ranging domestic sheep Ovis aries were common in the Norwegian part of the study area, but were not found in the Swedish part. Correction factors were used to correct for differences in digestibility and nutritional value of different foods. Because correction factors for ungulates are difficult to estimate, the results should be interpreted with some caution. In terms of digestible energy, ungulates, mostly carrion, were the most important food in both areas during spring. During summer, ants, forbs, and ungulates (reindeer Rangifer tarandus and moose Alces alces) were the most important food items in the Swedish area, and sheep were most important in the Norwegian area. The autumn diet was dominated by berries in the Swedish area and sheep and berries in the Norwegian area. Among berries, crowberry Empetrum nigrum was the most important species, followed by bilberry Vaccinium myrtillus in Sweden. The major difference between the Swedish and Norwegian areas was the large consumption of sheep in Norway, which provided protein and lipids, and was associated with a relatively reduced consumption of ants and forbs in summer and berries in the autumn. Based on different ingestion rates among the seasons, we estimated the relative contribution of major foods to total digestible energy. In the Swedish area, bears obtained 44-46 and 14-30% of their total annual energy from berries and ungulates, respectively. The remaining energy was obtained from insects (14-22%, mostly ants) and forbs and graminoids (12-18%, mostly blue sow thistle Cicerbita alpina). In Norway, bears obtained 65-87% of the energy from ungulates (mostly sheep), 6-17% from berries, 5-13% from insects, and 2-6% from forbs and graminoids. To gain weight prior to denning, brown bears in Norway selected lipid-rich and easily obtainable sheep in summer and autumn. In Sweden, they relied on carbohydrate-rich berries in autumn.
Key words: brown bear, correction factors, diet, domestic sheep, Norway, Sweden, Ursus arctos
Bjørn Dahle, Department of Zoology, Faculty of Chemistry and Biology, Norwegian University of Science and Technology, N-7034 Trondheim, Norway - e-mail: bjorn.dahle@chembio.ntnu.no
Ole Jakob Sørensen, Department of Resource Sciences, Nord-Trøndelag College, N-7701 Steinkjer, Norway
Egil Håvard Wedul, Østre Åsta, N-2430 Rena, Norway
Jon E. Swenson, Norwegian Institute for Nature Research, Tungasletta 2, N-7005 Trondheim, Norway
Finn Sandegren, Research Division, Swedish Hunters’ Association, Box 7002, S-75007 Uppsala, Sweden
Received 13 March 1997, accepted 12 April 1998
Associate Editor: Paolo Cavallini