Vulpes vulpes - Red Fox

Skull Pictures:      
Dorsal      Posterior mandible
Lateral      Ventral
Mandible

Physical Description:

The red fox (Vulpes vulpes) is a slender canid distinguished by its red or yellowish-red coat with white fur on the ventral part of the body (Kurta 1995).  The black legs and ear tips, as well as the white tip on the black-spotted tail can also be used to distinguish this species (Lariviere and Pasitschniak-Arts 1996).  In addition to the common red color phase, there are two rare color morphs, the cross and silver fox, that are displayed by different individuals (Lariviere and Pasitschniak-Arts 1996).  These individuals still have the characteristic black legs and a white-tipped tail, but the cross fox is distinguished by its yellowish to grayish-brown fur and black cross in the shoulder area (Kurta 1995).  The silver fox can be identified by its silver to black body depending on the amount of frost-like coloration, which results from the silver tips of guard hairs (Lariviere and Pasitschniak-Arts 1996).  In Wisconsin, the total length (head, body, and tail) of an adult red fox ranges from 975-1050 mm (38.4-41.3 in) with an average weight between 4.1 kg (9 lbs) and 5.9 kg (13 lbs) (Bluett 1984).  The length of the tail, hind foot, and skull are 300-405 mm (13.0-16.0 in), 160-175 mm (6.3-7.0 in), and 134-156 mm (5.3-6.1 in) respectively (Bluett 1984).  Generally the males have a larger average size than females (Lariviere and Pasitschniak-Arts 1996).

Distribution in Wisconsin:

Vulpes vulpes is present throughout the entire state (Bluett 1984).  The largest populations are found in the western, central, and southern parts of the state, while smaller populations inhabit the widespread forested areas of northern Wisconsin (Bluett 1984).  Historically, the probable distribution of native subspecies of Vulpes vulpes extended into northern Wisconsin (Kamler and Ballard 2002).  In the mid 1700’s, European settlers released the nonnative European red fox for sport hunting in the eastern United States (Kamler and Ballard 2002).  As more nonnative red foxes were released, the population grew and spread westward into the central part of the United States (Kamler and Ballard 2002).  Currently, the native species of red fox inhabit areas of higher elevation, while the nonnative red foxes inhabit agricultural, rangeland, and urban areas (Kamler and Ballard 2002).  Kamler and Ballard (2002) suggest that the nonnative red fox has replaced the once native fox of northern Wisconsin and makes up the widespread population of Vulpes vulpes currently in Wisconsin.  Overall, red fox populations have been relatively high since 1945, but expanding coyote (Canis latrans) populations may have caused recent numbers to decline (Bluett 1984).  

Ontogeny and Reproduction:

Vulpes vulpes is a monogamous species, and the male and female pair up in mid-December (Bluett 1984).  Females experience a single estrus period of 1-6 days in January or February and become sexually receptive for 2-4 days (Bluett 1984).  In southern Wisconsin, the mean conception dates are January 11-17 (Bluett 1984).  The gestation period for the red fox is about 53 days, and litter sizes range from 2-10, with the average Wisconsin litter size being 5.1 pups (Bluett 1984).  Litter size generally increases with food availability and with age of females (Lariviere and Pasitschniak-Arts 1996).  Pups are 152.4-203.2 mm (6-8 in) long and weigh 99.4-113.6 g (3.5-4.0 ounces) at birth, and by the time they are weaned, 8-10 weeks later, the pups weigh about 1.6 kg (3.5 lbs) (Bluett 1984).  Newborn foxes have dark grey fur with whitish brown feet (Lariviere and Pasitschniak-Arts 1996).  The grey fur changes to a pale buff color at 8-14 days and then changes to red at 9-14 weeks of age (Lariviere and Pasitschniak-Arts 1996).  The eyes of newborn foxes generally do not open until 3 weeks after birth, which is also around the time pups begin to walk (Lariviere and Pasitschniak-Arts 1996).  Both of the adults will assist in feeding the pups, and, at about 3 months of age, the juveniles will start to forage with the adults (Bluett 1984).  At 4-5 months, family bonds begin to diminish and dispersal usually occurs during October and November (Buett 1984).  Average juvenile male dispersal (29.6 km/18.4 mi) is greater then the average female dispersal (10.0 km/6.2 mi) (Buett 1984).  At approximately 10 months, foxes become sexually mature, with juveniles attaining full reproductive capacity 1-3 weeks after adults become sexually active (Buett 1984).

Ecology and Behavior:

The red fox prefers open areas with edge cover such as brushy fencelines, field-forest edges, or wooded stream and lake borders (Kurta 1995).  Vulpes vulpes is also found in residential suburbs, but tend to stay out of industrial and commercial areas (Lariviere and Pasitschniak-Arts 1996).  Strip cover, pastures, retired croplands, and hardwoods are all habitats were red fox dens are commonly found (Buett 1984).  Vulpes vulpes prefer a sand or gravel substrates for den constructions, and often enlarge existing woodchuck (Marmota monax) or badger (Taxidea taxus) dens (Buett 1984).

Prey availability plays a very important role in red fox habitat selection (Halpin and Bissonette 1988).  During winter, shifting snow conditions influence prey availability, which impacts habitat use and species preyed upon by red foxes (Halpin and Bissonette 1988).  The red fox is a fairly flexible predator and will prey on mammals, birds, fish, reptiles, invertebrates, and plants (Bluett 1984).  In southern Wisconsin, the main prey species of foxes are cottontail rabbits (Sylvilagus floridanus), meadow voles (Microtus pennsylvanicus), and white-footed mice (Peromyscus spp.) (Ables 1969).

Since the red fox has such a variable diet, it displays a number of different hunting behaviors.  In Wisconsin, red foxes are nocturnal, and they are most active at dusk and dawn throughout the year, with reduced relative amounts of nocturnal activity during the spring and winter (Ables 1969).  The activity patterns of red foxes overlap with the patterns of their prey, and males will travel an average of 14.5 km (9 mi) (females-9 km/5.6 mi) a night in search of food (Buett 1984).  When hunting small mammals, the red fox will use mainly sound to locate individuals and then use an aerial jump, as high at 4 m (13 ft), to pin the prey to the ground (Lariviere and Pasitschniak-Arts 1996).  Arboreal prey is captured by a quick horizontal thrust, and faster terrestrial prey is caught by stalking and chasing (Lariviere and Pasitschniak-Arts 1996).  A red fox will even attempt to nap near a burrow in which prey escaped and wait for it to re-emerge (Lariviere and Pasitschniak-Arts 1996).  Vulpes vulpes will also cache surplus food, and mark the caches with urine (Buett 1984).

The quality of habitat and the availability of food are both factors that affect the home range size of Vulpes vulpes.  In Wisconsin, foxes located in ecologically diverse habitats will have smaller home ranges (57.5 -161.9 ha/142-400 ac) than foxes in less diverse areas (up to 5 km2/2 mi2) (Buett 1984).  These home ranges are exclusive with non-overlapping borders and are actively defended, so they are considered territories (Lariviere and Pasitschniak-Arts 1996).  These territories are maintained throughout the year, but individual foxes become more tolerant during denning and rearing periods (Buett 1984).  Examples of more lenient behavior are: males and females will often share overlapping areas, territory boundaries far from the den are more flexible, and 2 females (1 dominant and 1 subordinate) may share the same home range to help raise a litter (Buett 1984).  Territories are marked with urine, and are aggressively defended by chases rather then physical contact (Lariviere and Pasitschniak-Arts 1996).

Along with scent marking and defense of territory, Vulpes vulpes also communicate through facial expressions and vocalizations (Lariviere and Pasitschniak-Arts 1996).  Urine marking serves as a dominance display, social record, and to mark remains while scavenging (Lariviere and Pasitschniak-Arts 1996).  Vocalizations are limited, but simple barking and growling can be used to produce more complex sounds (Lariviere and Pasitschniak-Arts 1996).  So far, research has show that vocalizations and facial expressions are secondary to scent marking for maintaining social bonds (Lariviere and Pasitschniak-Arts 1996).

The red fox has an average life span of only one year with a few that survive up to 5 or 6 years (Kurta 1995).  In Wisconsin, red foxes are exposed to a number of infectious diseases including: Leptospira grippotyphosa, canine distemper, canine hepatitis, staphyloccocus, tularemia, leptospirosis, California encephalitis, and La Crosse encephalitis (Buett 1984).  From 1967-1968, there was also an epidemic of Sarcoptic mange that was responsible for roughly 7% of the mortality in southern Wisconsin (Buett 1984).  Red foxes also carry rabies, but in Wisconsin only 3.1 % of confirmed rabies cases from 1970-1981 involved foxes (Buett 1984).  Rabies in the red fox is more of a concern in other parts of the world, and in Ontario, oral rabies vaccine baits are used to help control rabies (Rosatte 2002).  Heartworms are also know to be carried by foxes, and can pose a potential threat to domestic dogs (Buett 1984).  One suspected reason for the local transmission of infectious disease is the fact that communal denning (more than one family at a den) does take place in about 11% of dens in southern Wisconsin (Buett 1984).  Other causes of mortality include hunting, trapping, and roadkills (Buett 1984).

Literature Cited:

Ables, E.D.  1969.  Activity studies of red foxes in southern Wisconsin.  The Journal of Wildlife Management 33:145-153.

Alderton, D.  1998.  Foxes, wolves, and wild dogs of the world.  Blandford, UK.

Bluett, R.  1984.  Red Fox (Vulpes vulpes).  Wisconsin Department of Natural Resources Furbearer Profiles. 7:1-18.

Halpin, M.A., and J.A. Bissonette.  1988.  Influence of snow depth on prey availability and habitat use by red fox.  Canadian Journal of Zoology 66:587-592.

Kamler, J.F., and W.B. Ballard.  2002.  A review of native and nonnative red foxes in North America.  Wildlife Society Bulletin 30(2):370-379.

Kurta, A.  1995.  Red fox: Vulpes vulpes.  Pages 208-211 in Mammals of the great lakes region.  The University of Michigan Press, Ann Arbor, Michigan, USA.

Lariviere, S., and M. Pasitschniak-Arts.  Mammalian species: Vulpes vulpes.  American Society of Mammalogists 537:1-11.

Rosatte, R.C.  2002.  Long distance movement by a coyote, Canis latrans, and red fox, Vulpes vulpes, in Ontario: Implications for disease-spread.  Canadian Field-Naturalist 116(1):129-131.

Reference written by Derek Huebner, Biol 378: Edited by Chris Yahnke.
Page last updated  5-7-04.