Differences in mating system and group structure of
swift foxes also occurred between study sites. In the area of
low density (site 1), all adult groups consisted of monogamous
pairs with no nonbreeding females. In contrast, in
the area of high density (site 2), 30% of all adult groups
consisted of polygynous groups (two females and one
male), and nonbreeding females were present in 40% of
groups. Because mortality still occurred on site 2, mating
systems and group structures there were not homogenous
among family groups. Our results are similar to those of
Covell (1992), who found that polygynous mating groups
among swift foxes in Colorado occurred only when coyote
numbers were artificially reduced. During our study,
coyote numbers were reduced on site 1 during 2000