Red foxes mature sexually and produce a litter at about 1 year of age. Pups are blind and helpless at birth and remain with parents for roughly half a year. Red foxes typically pair monogamously.
Red foxes produce a single litter each year, typically in the spring. The vixen enters oestrus for 3 weeks, and she and the male mate several times during that period. Kits are usually born 49 to 58 days later. While litters of 13 kits are possible, most litters have roughly four to six offspring.
Kits are deaf and blind and lack teeth at birth, and they weigh less than 1/4 pound. Their eyes and ears begin to function at about 2 weeks of age. Red fox kits nurse for 3 to 4 weeks before the mother begins weaning them to solid food, although a vixen lactates for 6 weeks. By 6 to 7 months of age, fox kits reach adult size, and some vixens are reproductively mature at 9 months.
Most red foxes form monogamous pairs, and both males and females take part in caring for offspring. Help from the father is essential for the first several weeks as the mother remains with the kits to provide warmth. DNA analysis from some fox populations shows some amount of polygamy and incest.