Swift fox (Vulpes velox) COSEWIC assessment and status report 2009: chapter 3


Species Information

Name and Classification

Scientific name: Vulpes velox, Say 1823
English name: Swift Fox
French name: Renard véloce
Aboriginal names: Senopah (Blackfeet Tribe), Sinopaa (Blood Tribe)
Classification: Class – Mammalia
Order – Carnivora
Family – Canidae
Genus – Vulpes
Species – Vulpes velox

First described by Say (1823) as Canis velox (see Thwaites 1905), Swift Foxes were re–assigned to the genus Vulpes by Audubon and Bachman (1851). Swift Foxes and Kit Foxes (V. macrotis) are similar in appearance and Hall (1981) and Dragoo et al. (1990) suggested they were conspecific based on morphometric similarities and protein–electrophoresis. However, Mercure et al. (1993) demonstrated through mitochondrial DNA analyses that the sequence divergence between the two species is similar to that between other morphologically distinct canids – a conclusion that was supported by other morphometric analyses (Stromberg and Boyce 1986). Other than one narrow zone in eastern New Mexico and western Texas, where their ranges meet (Rohwer and Kilgore 1973), the topographic barrier of the Rocky Mountains separates the distributions of Kit and Swift Foxes. Although there has been known hybridization between the two species in this limited area, Thornton and Creel (1975) found the offspring to be of reduced viability. Merriam (1902) gave subspecific designations of V. velox hebes (northern Swift Fox; Canada and northern United States [US]) and V. velox velox (southern Swift Fox; southern range in US). Despite significant geographic variation in morphology within the species, however, these subspecific assignments are not likely valid (Stromberg and Boyce 1986).

Morphological Description

Swift Fox are the smallest North American canid, measuring just 70–88 cm in length (including the tail), standing 30–32 cm at the shoulder, and with a body mass of 1.6–3.0 kg (Kilgore 1969; Thornton and Creel 1975; Egoscue 1979; Harrison 2003) (Figure 1). On average, males are 8% larger than females (Egoscue 1979). Winter pelage is long and dense, with dark buffy–grey upper parts, orange–tan sides, legs, and ventral surface of the tail, with buff to pure white fur underneath; whereas summer pelage is shorter and more rufous (Nowak 1999). Swift Foxes have black patches on either side of the muzzle and a black–tipped tail. They do not exhibit sexual colour dimorphism (Chambers 1978). Unlike Red Foxes (Vulpes vulpes) and Arctic Foxes (V. lagopus), Swift Foxes in Canada are not known to exhibit distinct colour phases (Underwood and Mosher 1982; Cypher 2003).


Figure 1: Adult Swift Fox

Photo of an adult Swift Fox.

Photo © Gordon Court 2009.

Genetic Description

See discussion in Name and classification section on genetic and other information that serves to distinguish Swift foxes from Kit Foxes. Extensive genetic evidence suggests that apart from Kit Foxes, the closest relative to Swift Foxes are Arctic Foxes (e.g., Wayne and O’Brien 1987; Geffen et al. 1992; Mercure et al. 1993; Bininda–Emonds et al. 1999; Zrzavý and Řičánková 2004; Bardeleben et al. 2005).

Designatable Units

There are no known distinctions between populations within the species that would warrant consideration of separate designatable units. This report is therefore based on a single designatable unit of Vulpes velox.

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