The kit fox is a socially monogamous species, and the mated pair remains together throughout the year. However, Polygamous mating relationships have been observed. Female foxes begin searching for natal dens in September and October and usually usable dens are visited and cleaned of debris before the final selection is made. No nest as such is built, but new entrances and tunnels can be added to the den. As with most canids, copulation ends with a "tie" during which the penis is locked in the female's vagina.