The basic canid social unit is the monogamous pair, even in pack animals such as the wolf, where the alpha pair are the basis of the whole pack and usually the only animals to breed. Red foxes, coyotes and wolves are all seasonal breeders, whelping once a year. All have intricate courtship rituals involving the pursuit of the female by the male. Courtship may begin months before the female ever comes into heat, and pair bonds may last a lifetime. Copulation is terminated by a "tie", in which the bulbourethral process at the base of the penis swells into a knot which locks him inside the female for 5 to 30 minutes (this may allow time for sperm to fertilise the female, preventing other males from fertilising her). Male canids have a period of fecundity which approximately matches the females' estrous periods, and are infertile outside that time.
Wolves have a breeding season from January through April. Females are monoestrous; estrus lasts 5-15 days, with the alpha pair usually (but not always) being the only wolves in a pack to breed. Gestation lasts 60-63 days, with an average of 4-6 pups per litter, weaned in 5 to 8 weeks. All adults in the pack contribute to feeding the pups once they are weaned.
Although coyotes do not usually live in packs, they have an extended courtship period of 2 to 3 months. The female is monoestrous and is in heat from 2 to 5 days between January and March. Pairs bond for extended periods, often but not always for life. Gestation lasts from 60-63 days, with litters between 1 to 19 pups, averaging 6, at approximately 250 g apiece.
The estrous period of the fox is between 1 to 6 days, in December-January in the south of its range, in January-February in the central regions, and February-April in the north. Females may mate with a number of males but will establish a partnership with only one male. Gestation is between 51 and 53 days, with 1 to 13 pups (average: 5), between 50 and 150 g apiece, being born.
The preferred site for birth is a den which the female will begin digging usually around the beginning of courtship (although some wolf packs will occasionally keep the same three or four dens for years, and all three canids will take over dens dug by other animals). Pups are born covered with a "baby coat" of soft brown fur. They are blind, deaf, and helpless, able only to crawl with their forelegs and turn their heads in search of warmth and milk.
Females move their young between dens periodically to reduce the buildup of scent which comes
inevitably from the occupation. They grasp each pup individually by the loose skin at the back of
its neck, triggering an innate immobility reflex -- the pup goes limp until the mother puts it down.
Note the black mask and muzzle of the mother fox in the photo at left; this is a natural colour variation.
Development from this point is rapid,
with their eyes opening within three weeks, and many adult motor patterns appearing in the same
amount of time. Pups begin eating solid food at around three weeks. Both parents (or the entire
pack in the case of wolves) help to feed the pups. Canidae may carry food back in the mouth but
primarly carry food to pups in the stomach; pups lick the adult's mouth to stimulate regurgitation
of the food. This is a reflex; naive mature animals will display this behaviour when presented for
the first time with a puppy. Weaning occurs in between 1 and 2 months.
Sexual maturity may be reached before 12 months, although wolves and coyotes rarely breed before the second year. (Female foxes are sexually mature at 8 months old and may breed at that time.) Primarily, male pups disperse in C. latrans, female pups in C. lupus, and (almost) all pups in V. vulpes, with various exceptions.