American red fox

Current literature discusses whether or not the red fox is native to North America, with some research suggesting that nearly all red fox populations in North America are not native (Kamler & Ballard, 2002). Vulpes vulpes is usually seen either as an exotic species introduced by Europeans during the colonization of the North American continent or as a hybrid between Eurasian and native red foxes (Frey, 2013; Aubry et al., 2009). While it is claimed that Vulpes vulpes fulvus stems from a nonnative population that spread westward from European introduction (Kamler & Ballard, 2002), a historical analysis of firsthand accounts does not support this claim (Frey, 2013).

Phylogeographical and genetic analysis of the eastern American red fox suggests that foxes first migrated to North America during the Illinoian glaciation (300,000 to 130,000 years before present) and spread southward (Aubry et al., 2009) More recently, the Wisconsin glaciation (100,000 to 10,000 before present) separated the North American fox population into two distinct areas (Aubry et al., 2009). North American red foxes are genetically distinctive from their Eurasian counterparts (Aubry et al., 2009; Frey 2013). Despite claims of historical translocations from Europe, modern red fox populations in the United States’ southeastern region have been shown to be native to North America (Statham et al., 2012). DNA comparisons show that the eastern American red fox is closely related to native populations in Canada and the northeastern region of the United States and is therefore the result of natural range expansions and not an invasive species from Europe as was previously thought (Statham et al., 2012). Range expansions seen recently may be connected to anthropogenic landscape change and not the spread of exotic European varieties (Statham et al., 2012).

The native status of the eastern American red fox has been demonstrated by current research, which has important implications for management strategies. Previous classifications and taxonomic uncertainties (Kamler & Ballard, 2002) frame populations of Vulpes fulva as a non-native, invasive species that can cause declines in the populations of native species, carrying capacities, and populate regions at higher densities (Kamler & Ballard, 2002). The identification of the origins of the North American red fox populations is crucial in conservation efforts aimed at native vs. non-native species (Statham et al., 2012). In 2014 Statham et al released a study that supports Vulpes fulva as a separate species from the Eurasian Vulpes vulpes.

The North American red foxes have been traditionally considered either as subspecies of the Old World red foxes or subspecies of their own species, V. fulva. Due to the opinion that North American red foxes were introduced from Europe, all North American red foxes have been seen as conspecific with V. vulpes.[2] However, genetic analyses of global red fox haplotypes by Statham et al. (2012, 2014) indicates that North American red foxes have been genetically isolated from Old World populations for 400,000 years, prompting possible application of V. fulva to all North American red foxes.[3][4] Castello (2018) has formalized treatment of Vulpes fulva as a separate species from the nominate Vulpes vulpes from the Old World.[5]

Red foxes colonized the North American continent in two waves: before or during the Illinoian glaciation, and during the Wisconsinan glaciation.[6] Gene mapping demonstrates that red foxes in North America have been isolated from their Old World counterparts for over 400,000 years, thus raising the possibility that speciation has occurred.[7] In the far north, red fox fossils have been found in Sangamonian deposits in the Fairbanks District and Medicine Hat. Fossils dating from the Wisconsian are present in 25 sites in Arkansas, California, Colorado, Idaho, Missouri, New Mexico, Tennessee, Texas, Virginia, and Wyoming. Although they ranged far south during the Wisconsinan, the onset of warm conditions shrank their range toward the north, and they have only recently reclaimed their former American ranges because of human-induced environmental changes.[8] Genetic testing indicates two distinct red fox refugia exist in North America, which have been separated since the Wisconsinan. The northern (or boreal) refugium occurs in Alaska and western Canada, and consists of the large subspecies V. v. alascensis, V. v. abietorum, V. v. regalis, and V. v. rubricosa. The southern (or montane) refugium occurs in the sub-alpine parklands and alpine meadows of the Rocky Mountains, the Cascade Range, and the Sierra Nevada, and consists of the small subspecies V. v. cascadensis, V. v. macroura, V. v. necator, and V. v. patwin. The latter clade has been separated from all other red fox populations since the last glacial maximum, and may possess unique ecological or physiological adaptations.[6]

Although European foxes (V. v. crucigera) were introduced to portions of the United States in the 1900s, recent genetic investigation indicates an absence of European fox haplotypes in any North American populations.[9] Also, introduced eastern American red foxes have colonized southern California, the San Joaquin Valley, and the San Francisco Bay Area, but appear to have mixed with the Sacramento Valley red fox (V. v. patwin) only in a narrow hybrid zone.[10] In addition, no evidence is seen of interbreeding of eastern American red foxes in California with the montane Sierra Nevada red fox (V. v. necator) or other populations in the intermountain West (between the Rocky Mountains to the east and the Cascade and Sierra Nevada Mountains to the west).[11]

Castello (2018) recognized nine subspecies of the North American red fox, as listed below:

An eastern American red fox in its winter coat

Vulpes vulpes fulvus inhabits the entire region of the United States east of the Rocky Mountains except the southern Great Plains and southern Texas (Frey, 2013; Tesky, 1995). The eastern American red fox generally prefers mixed vegetation communities that occur on edge habitats with a high level of diversity (Tesky, 1995). In developed areas, the eastern American red fox will inhabit areas that offer a combination of woodland and agricultural land (Tesky, 1995).

The eastern American red fox has a primarily carnivorous diet dominated by small mammals (Frey, 2013). However, as an opportunistic species they will adopt an omnivorous diet that includes insects, fruits, berries, birds, plants, and other small animals (Tesky, 1995). Food sources can vary depending on region, but cottontail rabbits (Sylvilagus) are the most important prey for eastern American red foxes (Frey, 2013). The eastern American red fox will consume larger animals as carrion, and their diet changes depending on seasonal variability (Tesky, 1995).

• Aubry, K.B.; Statham, M.J.; Sacks, B.N.; Perrine, J.D.; Wisely, S.M. (2009). "Phylogeography of the North American red fox: Vicariance in Pleistocene forest refugia". Molecular Ecology. 18 (12): 2668–2686. doi:10.1111/j.1365-294x.2009.04222.x. PMID 19457180.
• Frey, J.K. (2013). "Re-evaluation of the evidence for the importation of red foxes from Europe to colonial America: Origins of the southeastern red fox (Vulpes vulpes fulva)". Biological Conservation. 158: 74–79. doi:10.1016/j.biocon.2012.07.027.
• Hall, E.R. (1981). The Mammals of North America Vol. 2. 2nd ed. New York: John Wily and Sons.
• Kamler, J.F.; Ballard, W.B. (2002). "A review of native and nonnative red foxes in North America". Wildlife Society Bulletin. 30 (2): 370–379.
• Statham, M.J.; Sacks, B.N.; Aubry, K.B.; Perrine, J.D.; Wisely, S.M. (2012). "The origin of recently established red fox populations in the United States: translocations or natural range expansions". Journal of Mammalogy. 93 (1): 52–65. doi:10.1644/11-mamm-a-033.1.
• Tesky, J.L (1995). Wildlife species: Vulpes vulpes. U.S. Department of Agriculture and Forest Service. Retrieved from: http://www.fs.fed.us/database/feis /animals/mammal/vuvu/ all.html#36

Wikispecies has information related to Vulpes vulpes fulvus.