Typically foxes will have several dens in close proximity so that if danger, perceived or real arises, they can move their young to a safer site. A den site usually has two entrances, some have three. Foxes may tolerate a lot of disruption, or they may move at the first hint of disturbance. Henry (1996) records unwittingly causing a female to move her young when he “crossed an invisible but important vulpine boundary” in his attempt to get photographs. In 1982, Theresa Ani kowicz (1983) came across a vixen moving her cubs from one den to another near Ramsayville Marsh. She was able to carefully watch, follow and photograph this family over the course of the summer, from the time the cubs were tiny and still without their red pelage, until they grew old enough to be more wary of the world.
Some den sites may be occupied for many years. Several sites on the CEF have been used for at least a decade, probably longer and the animals seem to alternate use every few years.
During the winter, dens will be cleaned out or modified, in preparation for birth. New dens may be dug by the foxes, but often as not they will take over an old groundhog burrow and enlarge it. I know that at least three of the den sites I’ve found on the CEF have been previously used by groundhogs. I don’t know if the dens were still occupied by groundhogs when the foxes took possession. However, Banfield (1974) notes “an unusual interspecific tolerance between the red fox and the woodchuck, with both species occupying the same burrow, has been described.” No doubt this is a rare occurrence given that groundhogs are a favoured prey item! Hollow logs are sometimes used as dens. Elbroch (2003) says entrances may be anywhere from 15 to 30.5 cm in diameter. The dens I’ve measured on the farm, including FWG, have ranged from 15 cm to more than 45 cm in diameter.
At the FWG, there are several very old sites, probably used in the days before the area became so busy and disturbed. One is enclosed in what is now a thicket of trees and shrubs. This particular den had several entrances, one quite large. Another den was on a steep slope, invisible to most people, well protected by trees. Yet another den was under a clump of conifers, but has since almost vanished, filled in by leaves, needles and other debris.
Gestation takes about 51 days (Banfield 1974, Forsyth 1985, Henry 1996). The kits or pups, weigh approximately 100 g when born (Banfield 1974) and are dark gray, charcoal, or dark brown. During the 1970s, in the Dunrobin area, I found a fox den in a hollow log; nearby was a dead kit, probably not more than a couple of weeks old. It was entirely black. According to most sources, the pups are blind and helpless for the first 10 days. However, they develop quickly and in no more than a month are able to leave the den. It is not uncommon to see them playing around the site, always under the watchful eye of mother. By this time, they have attained the orangey-red pelage that we associate with the species. One year I counted five youngsters at a den site on the CEF, but typically I have not seen more than three or four. Banfield (1974) and others give the average litter size as five.