Foxes are solitary except during the winter breeding season through midsummer, when mates and their young closely associate.
Red foxes reach sexual maturity within 1 year. Red foxes normally mate from mid-January to early February and produce 1 litter per year. Estrus lasts 1 to 6 days, followed by a 51- to 53-day gestation period. Fox pups are born from March in the south, to May in the arctic. Red foxes generally produce 4 to 9 pups per litter, and gray foxes usually have 3 to 7 pups.
Foxes disperse from denning areas during the fall and establish breeding areas in vacant territories, sometimes dispersing up to 245 miles.
Red foxes dig their own dens or use abandoned burrows of woodchucks or badgers. The same dens often are used for several generations. Dens may be located near farm buildings, under haystacks, and inside hog lots or small pastures used for lambing. Gray foxes commonly create dens in wood piles, rocky outcrops, hollow trees, and brush piles.
Foxes are crepuscular (active primarily during twilight). They also move about during the day, especially when it is dark and overcast. Foxes are active year-round, and foraging tends to increase with the birth of young in the spring. Gray foxes can climb trees.
Red foxes adapt to most habitats within their range, but usually prefer open country with moderate cover. The highest densities of foxes have been reported in the north central US, where suitable habitat is interspersed within extensive farmlands. Red foxes have established breeding populations in urban areas of the US, Canada, and Europe.
Gray foxes prefer more dense cover such as thickets, riparian areas, swamps, and rocky pinyon-cedar ridges. In eastern North America, gray foxes are closely associated with edges of deciduous forests. Gray foxes also are found in urban areas where suitable habitat exists.
Foxes are opportunist feeders that eat rabbits, mice, birds, eggs, insects, and fruits. Foxes usually kill animals that are smaller than a rabbit, although raccoons, opossums, fawns, piglets, kids, lambs, and poultry sometimes are killed and eaten. Foxes have a keen sense of hearing, vision, and smell that aid them in the detection of prey. Foxes stalk even the smallest prey with skill and patience, usually ending with a sudden pounce. Red foxes sometimes kill more than they can eat and bury food in caches to eat later. All foxes feed on carrion.