Breeding occurs from December to February, and most litters are born in March or early April. Litter size varies from three to six and the swift or kit fox is monestrous. The den is a simple structure with one or more openings. One that Cutter excavated had a circular entrance 20 cm in diameter and a total of 378 cm of open, underground tunnel. Three dens were as close as 85 m to human habitation.
Swift foxes are relatively unafraid of man and are far less cunning than most other foxes.
They are so unsuspicious that they are easily trapped, and even more easily poisoned. Consequently, wherever trappers are active, and especially wherever control campaigns involving the use of poison have been carried out against predatory animals on areas inhabited by swift foxes, the foxes have been greatly reduced in number or entirely eliminated. However, in a recent taxonomic study of these foxes using advanced morphometric and protein-electrophoretic methods, Dragoo and colleagues concluded that these taxa are not sufficiently distinct to warrant separate specific status. Thus, the two foxes are now grouped into a single species, Vulpes velox , comprised of two sub-species, V. v. velox and V. v. macrotis .