Northern Prairie Wildlife Research Center
Habitat and History. The red fox is adapted to prairie environments and to coexistence with humans (Sargeant 1982; Voigt 1987). Habitats throughout the prairie pothole region seem suited to this species, even though the geographic range of the red fox does not include portions of south-central Alberta and western Saskatchewan (Hall 1981). The red fox was sparsely distributed throughout the region before settlement and may have been less abundant than gray wolves or coyotes (Farley 1925; Bailey 1926). Red fox populations seemingly increased for a short time after settlement began (Seton 1909; N. Criddle 1929; S. Criddle 1929; Baines 1969; Sargeant 1982) but then declined. From the 1890's to mid-1930's, red foxes were scarce or absent throughout most of the region (Bailey 1926; S. Criddle 1929; Bird 1930, 1961; Soper 1946,1961; Sargeant 1982). Beginning in the 1930's in the United States and in the late 1950's in Canada, red fox populations expanded greatly, especially in the eastern half of the region (Bird 1961; Dekker 1973; Johnson and Sargeant 1977; Stelfox 1980; Sargeant 1982; Jorgenson 1987).
Red foxes in the prairie pothole region have been subjected to the same human-caused mortality as coyotes but, in general, have not been affected as severely, probably because of differences in species biology. Red foxes tend to occupy much smaller home ranges than coyotes (individual foxes are exposed to fewer humans than individual coyotes), and red foxes have higher reproductive rates than coyotes . Most red foxes breed during their first year of life (Voigt 1987), whereas many coyotes do not breed until their second year (Voigt and Berg 1987). Nevertheless, during periods of exceptionally high fur pelt prices, human-inflicted mortality profoundly reduced abundance of red foxes in the region (Sargeant 1982).
Population Structure. Red fox populations in spring are composed of family groups, usually a mated pair, but sometimes include additional adults (Sargeant 1972; Ewer 1973; Voigt and Macdonald 1984). Family groups occupy relatively discrete territories ranging from about 3 to 21 km2 in rural areas but generally <12 km2 (Sargeant 1972; Sargeant et al. 1987a; Voigt 1987; Trewhella et al. 1988). Territory size seems to be inversely related to population size (Sargeant 1972; Trewhella et al. 1988)). In the absence of coyotes, territories of red foxes tend to be contiguous and largely non-overlapping (Sargeant 1972; Voigt and Macdonald 1984; Mulder 1985). When coyotes are present, territories of red foxes tend to be discontinuous and around the periphery of territories of coyotes (Voigt and Earle 1983; Sargeant et al. 1987a).
Distribution and Abundance. Red foxes were present each year in all except two study areas (Gayford; Hay Lakes in only 1984) in the western edge of the prairie pothole region (Appendix Table 5). The finding of up to nine rearing dens of at least four red fox families in individual study areas (Appendix Table 8) indicated that populations in several areas were comparable to the relatively high populations reported from other parts of North America and from portions of the prairie pothole region during other times (Sargeant 1972; Sargeant et al. 1975; Voigt 1987).
In general, the abundance of red foxes decreased from southeast to northwest across the region (Fig. 7). Red foxes were common or more abundant in a greater percentage of study areas in the United States than in Canada (Appendix Table 6) and in a greater percentage of study areas in the prairie than in the aspen parkland (Appendix Table 7). In the United States, they were numerous in nine study areas (53%) and common in all others. In Canada, they were numerous in two study areas (13%), common in nine (56%), and uncommon or less abundant in five (31%). The removal of predators from three study areas (Eldridge, Fredonia, Lake Park) probably had no effect on the counts of red fox tracks. The first searches for tracks in those study areas were largely completed before any red foxes were captured, and tracks of red foxes continued to be found in quarter sections where trapping was conducted after red foxes were removed. Red foxes expand their territories to include adjacent areas soon after neighboring red foxes die (Sargeant 1972).
The highest indicated populations of red foxes were in study areas with the fewest coyotes (see section on Inter- and Intraspecific Interactions); these were also the most intensively farmed areas. Red foxes were especially abundant in study areas in western Minnesota and eastern North Dakota where they were numerous in 8 of 11 areas (Fig. 7). A notable exception to progressively fewer red foxes toward the northwest was one study area (Denzil) in western Saskatchewan where tracks were found in 88 and 97% of searched quarter sections during the 2 study years (Appendix Table 5). Of the study areas in Canada, this study area (Denzil) was one of the most intensively farmed (Table 1) and had one of the lowest coyote populations (Fig. 5).
Red foxes were absent from portions of many study areas in Canada, and in three of those study areas (Hay Lakes, Holden, Yorkton) tracks were found in only 2 or 3 quarter sections (Appendix Table 5), indicating occasional visits to a small part of each area. In most other study areas with tracks of red foxes in <50% of searched quarter sections, the quarter sections with tracks were clustered and often an active red fox rearing den was in one or more of the clusters (Hanley in 1984; Leask in 1984 and 1985; Penhold in 1985). Only one or two red fox families occupied portions of each of those study areas. The occupied quarter sections were always in intensively farmed areas and usually near farmsteads and well-traveled roads.
Fig. 7. Percentage of searched quarter sections (in black) by study area in which red fox tracks were found or in which the abundance of tracks was estimated during two systematic annual searches in April-June in greater than or equal to 1 study year (Appendix Table 5) and ratings of the abundance of red fox in each area, 1983-88. Results for study areas searched >1 year were averaged; study areas are in the prairie pothole region.