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Individual study: Winter food provision enhances den occupancy and litter production of Arctic foxes Alopex lagopus in Vindelfjallen nature reserve, Västerbotten, Sweden

Published source details

Angerbjorn A., Arvidson B., Noren E. & Stromgren L. (1991) The effect of winter food on reproduction in the arctic fox Alopex lagopus: a field experiment. Journal of Animal Ecology, 60, 705-714


The mainland Arctic fox Alopex lagopus population of Scandinavia is small and declining in spite of legal protection afforded for over 50 years; the reasons for a lack of recovery following protection are unclear. As a potential conservation measure, this study investigated the effect of providing additional food on reproductive success of Arctic foxes in Swedish Lapland.

Study area: The study was undertaken primarily in the Vindelfjallen nature reserve in the county of Vasterbotten, 66ºN, 16ºE, northern Sweden.

Food provision: During the winter months (January-April) of 1985-1989, remains of reindeer Rangifer tarandus and moose Alces alces carcasses (from road accidents) were cut into small pieces, and placed 50-200 m from a den which showed signs of Arctic fox activity. Checks were made after 1-3 nights, tracks from foxes showed that all pieces had been taken and cached in new places. Additionally, food was supplied by digging the food down 1-2 m in the snow, where foxes could reach it via a tunnel.

Over the five study years, 65 dens were located, 15 of which were never occupied. Of those occupied, 10 were provided with food in all winters, and nine were in a 'mixed group' (i.e. one year a food den and the next a no food control den).

Monitoring of litter size: Food-manipulated and control dens were monitored during July to assess if dens were occupied, and if so, the number of fox cubs in each litter.

Of the 103 control dens (i.e. control dens accumulated over the 5 years), only about 6% were ever occupied. In contrast, of the 65 food dens 35% were occupied.

Over the five summers, there were only three arctic fox litters found in the 103 control dens (3%), but 17 of 65 food dens contained a litter (26%). However, no effect of food provision on litter size was apparent: food dens average 5.24 cubs (n = 17); control dens average 5.67 cubs (n = 3).

Based on these study results, the authors conclude that the extra winter food increased both the number of breeding attempts (i.e. foxes staying at one den), and successful breeding attempts (i.e. number of fox cubs produced).

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