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The Swedish Arctic Fox Project has been studying the behavioural ecology, population dynamics and conservation issues of the arctic fox Alopex lagopus since 1985 (Hersteinsson et al. 1989, Angerbjörn et al. 1991). The study area comprises 2100 km2 of subarctic mountain tundra in the Nature Reserve of Vindelfjällen, Sweden (66°N, 16°E), 750–1400 metres above sea level. Most of the study site consists of dry grass heath, meadows and willow wetlands with low plant species diversity, although there are patches with higher diversity. Water is abundant in lakes and streams during the summer months.

With the aid of volunteers, information on this arctic fox population is collected through den inventories, behavioural observations, radio telemetry and captures of juveniles and adults. Captures are primarily made within a core study area of 540 km2 and involve tagging, weighing and measuring of the animals. All captures are made on or near dens in metal cage traps with 9"–15" openings, baited with dog food pellets or fish. Traps are kept under constant observation when open. All captures and most inventories are made during the breeding season, from July to September, with additional field work in winter and spring.

We follow all litters within the core study area from emergence in early July until August or September. Of all 253 cubs born within the core area in 1985–1997, 90% were eartagged as juveniles. An additional 88 juveniles were tagged in the surrounding areas. We have fitted 46 adults and older juveniles with radiocollars (Angerbjörn et al. 1997). Thus, we have been able to follow a relatively large number of breeding individuals closely, often for many seasons. This is aided by the extent of the study area, the large number of people involved and the fortunate combination of 24 hour daylight and a carnivore with little fear of humans.

Within the Vindelfjällen project, we have also performed feeding experiments in the field. In two sets of experiments, additional food was supplied at dens in late winter and in summer, respectively (Angerbjörn et al. 1991, Tannerfeldt et al. 1994). Winter feeding was performed each year 1985–1993 and summer feeding 1990–1997. We then analysed the effects on breeding performance and juvenile survival (Tannerfeldt et al. 1994, Angerbjörn et al. 1995). Both winter and summer feeding was substantial, but it only provided a supplement to the natural food of the foxes. Adults continued to hunt and when rodents decreased in numbers, many cubs starved despite our feeding.

The results of the study have been published in both scientific and popular articles, listed here.

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