Shortly after the last season´s cubs have dispersed, the males begin producing sperm. By October or November there is a notable rise in the aggressiveness of the male animals. Scent marking of the home territory´s boundaries increases in both frequency and intensity; by the beginning of the mating season these marks will have taken on a strong, musky, skunk-like odour. This scent will tell members of both sexes that there are interested parties in the area. It is at this time, when the males are vying for a chance to reproduce, that conflict amongst adult foxes is at its highest and fighting may sometimes result in serious injuries. By the end of these contests, the victor will have won the right to mate with any vixens in his range.

A dog fox and its potential mate will occasionally encounter one another in their territories. Earlier in the season they will take notice of one another but with only limited interest. As time goes on, they will spend increasingly longer amounts of time with one another, and their normally solitary footprints become paired tracks in the snow. They engage in affectionate play, spend time in close contact with each other, and generally get to know more about their mates. Hunting is still conducted as a solitary activity, but even then the fox and vixen will maintain vocal communication between themselves over their range. Red foxes are typically monogamous inasmuch as that they very rarely have more than one mate per season. They are also well known for the same breeding pairs remaining together for several years, especially in areas where the fox population is sparse.

The relationship eventually culminates in a mating between the pair in January or February. The breeding occurs at a time such that the kits will be born as early as possible once the mild spring weather has arrived. In southern climates the mating can occur as early as December to take advantage of earlier spring´s, while in the north it may be delayed as late as March. Depending on the location, kits could therefore be born anywhere between February and May. The actual mechanism behind this timing appears to be the based on the amount of daylight the vixen is exposed to; as the days decrease and then increase in length with the seasons, her reproductive cycle is effected. Regardless of when they come into heat, the vixens will remain in estrous for only about three days, at which time mating must occur. The mating itself is typically canine in fashion with the male mounting the female from the rear to deposit his sperm.