Selection of natal dens by the swift fox (Vulpes velox) on the Canadian prairies

Abstract

The location and physical characteristics of 32 occupied swift fox (Vulpes velox) natal/rearing dens and 33 unoccupied sites in southeastern Alberta and southwestern Saskatchewan, Canada, were compared in 1991 and 1992. Comparisons between occupied and unoccupied sites were restricted to eight habitat variables that described the orientation of each den entrance, mean height of old and new grass, number of holes in each den complex, den position and slope (i.e., incline of the land) in relation to hills, and distance to the nearest roadway and water source. Two-sample t tests and Mann-Whitney U tests indicated that occupied sites were located on the tops of hills, close to roads, and in places where old grass was significantly higher than at unoccupied sites. Den entrance angles did not differ between occupied and unoccupied sites. A stepwise discriminant function analysis identified five potential discriminators of occupied and unoccupied sites (i.e., position on a hill, height of new grass, distance to water, distance to roads, and slope). Den position was the variable that discriminated most strongly between occupied and unoccupied sites. Occupied sites were located predominantly on the tops of hills. The quadratic discriminant function had an overall classification success of 83.1%. Based on the five habitat variables, the discriminant function model correctly classified 28 of the 32 occupied sites as being occupied (87.5%) and 26 of the 33 unoccupied sites as being unoccupied (78.8%). The habitat variables identified by the discriminant function model may be a useful tool for selecting and modifying release-site characteristics and creating more realistic live-rearing facilities.

Multiple Scale Den Site Selection by Swift Foxes, <em>Vulpes velox</em>, in Southeastern Colorado

“…Denning might enable Swift Foxes to maintain homeostasis by providing a cool, damp microhabitat refuge. Dens offer shelter from the elements and facilitate escape from predators, especially Coyotes (Canis latrans), in an environment that offers little natural cover (Egoscue 1979;Rongstad et al1989;Herrero et al 1991;Pruss 1999). Kitchen et al (1999) found all Coyote-killed Swift Foxes near the periphery or outside their home range boundary, a significant distance from their nearest currently used den.…”

“…Thus, knowledge of habitat requirements for den sites might be an important component of Swift Fox conservation efforts (Hillman and Sharps 1978;Pruss 1999); however, results of studies on Swift Fox den site selection have varied. Swift Foxes may modify burrows dug by other animals such as American Badgers (Taxidea taxus), ground squirrels (Spermophilus spp.)…”

“…Swift Foxes may modify burrows dug by other animals such as American Badgers (Taxidea taxus), ground squirrels (Spermophilus spp.) or Black-tailed Prairie Dogs (Cynomys ludovicianus), or dig their own dens (Kilgore 1969;Hillman and Sharps 1978;Cameron 1984;Pruss 1999). Dens have been found in a variety of habitat types including shortand mid-grass prairie, grazed prairie, cultivated fields, fence rows, and rock outcrops (Cutter 1958;Hines 1980;Cameron 1984;Uresk and Sharps 1986;Rongstad et al 1989;Pruss 1999).…”

“…or Black-tailed Prairie Dogs (Cynomys ludovicianus), or dig their own dens (Kilgore 1969;Hillman and Sharps 1978;Cameron 1984;Pruss 1999). Dens have been found in a variety of habitat types including shortand mid-grass prairie, grazed prairie, cultivated fields, fence rows, and rock outcrops (Cutter 1958;Hines 1980;Cameron 1984;Uresk and Sharps 1986;Rongstad et al 1989;Pruss 1999). Occasionally, dens have been associated with man-made structures such as culverts, buildings, and cemetery gravesites with a concrete cap (Kilgore 1969;Hillman and Sharps 1978;Jackson and Choate 2000 (Hillman and Sharps 1978;Cameron 1984;Uresk and Sharps 1986;Pruss 1999;Harrison 2003).…”

“…Dens have been found in a variety of habitat types including shortand mid-grass prairie, grazed prairie, cultivated fields, fence rows, and rock outcrops (Cutter 1958;Hines 1980;Cameron 1984;Uresk and Sharps 1986;Rongstad et al 1989;Pruss 1999). Occasionally, dens have been associated with man-made structures such as culverts, buildings, and cemetery gravesites with a concrete cap (Kilgore 1969;Hillman and Sharps 1978;Jackson and Choate 2000 (Hillman and Sharps 1978;Cameron 1984;Uresk and Sharps 1986;Pruss 1999;Harrison 2003). However, dens also have been found in level, open areas and at the base of hills (Kilgore 1969;Hines 1980;Cameron 1984).…”