Fox populations: North America

Fox standing a tree log
A red fox

Red foxes are native in North America and can be found throughout the United States and Canada except in the far north, where the arctic fox (scientific name Alopex lagopus) is better adapted to live, and in some parts of western United States. Foxes from Europe were also introduced repeatedly in various parts of the continent for fur farming and fox hunting. Releases occurred in Alaska, California, in south-eastern, eastern and central states.

Historically, native red foxes occupied the northern regions of North America and mountain areas at high elevations in the western USA. Introductions of European red foxes occurred in the eastern USA and in lowland areas on the Pacific coast. At the beginning of the 20th century, red foxes expanded into central and eastern states where they had not been recorded historically, leading researchers to conclude that these were non-native red foxes, introduced from Europe. Some authors also argued that non-native red foxes occur at higher population densities and are better adapted to live in human disturbed environments, such as urban areas, than native American red foxes.

However, recent genetic studies, as yet unpublished, have suggested that this post-European expansion of red foxes in the United States was due to the spread of native foxes southward from Canada, following the clearing of forests for agriculture, changes in the predator community, and other major habitat changes in the region. It seems that the introduced European foxes made at best only a minor contribution to the fox population seen in mainland North America today.

Appearance

Close up of a fox facewith a dark colouration on its neck fur
A red fox with a dark colouration

Red foxes from North America are comparatively light with larger sexual dimorphism than Eurasian red foxes. This has led some authors to consider this red fox to be a different species or sub-species (scientific name Vulpes fulva) from the Eurasian red fox (scientific name Vulpes vulpes). In North America, black foxes are relatively common. Black foxes are known as silver foxes as the hair on the rump is tipped with silver and this is very conspicuous against the black fur. A variant that is only present in North America is the cross fox. Cross foxes have a prominent black stripe along the spine and a stripe along the shoulders at a right angle, which gives the appearance of being a cross.

Predation

A young duckling
Foxes predate on ducks

Predation by red foxes significantly reduces the number of ducks in the midcontinent area of USA. A study investigating duck remains found at fox dens found that at least seven duck species were consumed by foxes: blue-winged teal (scientific name Anas discors), mallard (A. platyrhynchos), northern pintail (A. acuta), northern shovelers (Spatula clypeata), gadwalls (A. trepera), green-winged teals (A. crecca) and American wigeons (A. americana). Of all adult duck remains found at fox dens, 76% were hens. The study concluded that, each year, the average annual take of adult ducks by foxes in this region amounts to approximately 900,000. This number included ducks killed and also scavenged by foxes.

Other bird populations reduced by fox predation in the Great Basin region in USA are pheasants (scientific name Phasianus colchicus) and sage grouse (Centrocercus urophasianus).

Urban life

A study in suburban Toronto, Canada, found that foxes lived in groups that contained both breeding and non-breeding females. Fox territories included golf courses and park land as well as low-density housing. However, in contrast to mainland Europe and Great Britain, foxes avoided medium-density housing areas, suggesting that they might not have been used to urban life.

Websites of interest

There are a lot of useful external websites on foxes. The ones listed here have general and more specific information and images about foxes in the USA and Canada:

References

  • Adkins, C. & Stott, P. (1988). Home ranges, movements, and habitat associations of red foxes (Vulpes vulpes) in suburban Mississauga, Ontario, Canada. Journal of Zoology 244, 335-346.
  • Kamler, J.F & Ballard, W.B (2002) A review of native and nonnative red foxes in North America. Wildlife Society Bulletin 30, 370-379.
  • Lewis, J.C., Sallee, K.L. & Golightly, R.T. (1999) Introduction and range expansion of nonnative red foxes (Vulpes vulpes) in California. American Midland Naturalist 142, 372-381.
  • Sargeant, A.B., Allen, S.H. & Eberhardt, R.T. (1984) Red fox predation on breeding ducks in midcontinent North America. Wildlife Monographs 89, 1-41.,
  • Swanson, B.J., Furhmann, R.T. & Crabtree, R.L. (2005) Elevational isolation of red fox populations in the Greater Yellowstone Ecosystem. Conservation Genetics 6, 123-131.