Foxes undergo a specific reproductive phase known as “in heat” or estrus. This period is fundamental for their breeding cycle, signaling the female’s readiness to mate and ensuring the continuation of the species. Understanding this phase is important for observing fox behavior in the wild.
Understanding the Breeding Season
The breeding season for foxes typically occurs once a year, primarily during late winter to early spring. In the Northern Hemisphere, most matings take place from January to February, though this can extend from late December through March. Foxes in southern regions may breed earlier, while those in northern, colder climates might breed later, even into April.
A female fox, known as a vixen, becomes sexually mature at around 10 months of age. The actual estrus period, when the vixen is receptive to fertilization, is relatively short, usually lasting between one and six days. Although the broader “oestrous” cycle can last for about three weeks, the critical window for successful mating is brief within this period. Foxes are monoestrous.
Observable Signs of Readiness
During the breeding season, several physical and behavioral changes indicate a vixen’s readiness to mate. Vixens often emit high-pitched, unearthly screams, which can sound similar to a human in distress. These “vixen screams” are primarily used to attract male foxes, known as dog foxes, and signal their receptiveness.
Dog foxes respond with barks, and both sexes become much more vocal than usual. Beyond vocalizations, foxes communicate through scent marking, which plays a role in mate searching. Dog foxes may lift their tails high as a vixen approaches estrus. Increased activity and interactions between males and females, including male foxes trailing vixens, also become more frequent.
The Mating and Denning Process
Once a vixen is in estrus, mating occurs. Foxes often form pairs, and while they may bond and travel together for several weeks leading up to mating. The actual copulation can involve a “copulatory tie,” where the male and female become temporarily locked together due to the swelling of the male’s bulbus glandis and contraction of the vixen’s vagina. This tie can last from a few minutes to over an hour.
After successful mating, the gestation period typically lasts around 51 to 53 days, with an average of 52 days. Vixens give birth to a litter of kits, usually between March and April. Litter sizes can vary, but generally average around four to five pups. The vixen will select or prepare a den, often an abandoned burrow of another animal or one she digs herself, to give birth and raise her young. The male fox often assists by bringing food to the vixen while she remains in the den.