Wild canids mate once a year, towards the end of winter. Around two months later, usually after 9 weeks or 63 days, the cubs are born. Unlike wild females, domestic dog females are in heat twice a year, but the pregnancy lasts the same amount of time.
Heat
Females have their first heat about nine months old, but it can be sooner as well as later. Wolves in captivity will begin with reproduction when nine or ten months old, while the first litter will come when female is 2 to 5 years old. Alpha couple usually mates 3–4 years.
Before the first heat there is proestrus cycle. This cycle makes female reproductive organ swell and begin its activity. It lasts around nine days and female will become more unsettled during this period. She will be prone to roaming more than usual. She would drink and urinate more often. The scent of the urine will attract males that can smell it from afar. Although she releases inviting scents, the female will reject males that try to win her over. She will be determined, showing it by growling, showing the teeth, chasing them or even going for a bite. Less aggressive female will usually just run or turn away from a male that tries to mount her, while some would just sit down. Unlike with human females, dog females bleed before the ovulation, preparing for it. It is followed by heat or sexual receptiveness, formally known as estrus. This is a latin term that means "sexual desire". The heat period lasts 21 days, sometimes a day longer or shorter. In this state, female is more active, even aggressive at times. Fertile period last only a few days, when ovulation begins, it takes around 72 hours for eggs to mature when they can be fertilized.
Courting
Before mating, male will follow female closely and court her in any way and very persistently: running around her, turning, circling her, staring at her, sniffing her, barking as if he is begging, grooming her, licking her (mostly her ears)... With long sniffing of her rear end he intensifies his intention. That is the moment when female decides. If she is interested, she will display her rear end and move her tail aside. At this gesture, male will approach her sideways and set his head on her back. If she does not pull back but remains still, the male will mount her.
Because of its solitary life, a fox will make unpleasant yip, during mating period as a call for a mating partner. Then, usually, several males will join a female, follow her and court her as other dogs do. At this period they will bark more often than usual, while jackals will howl.
The wooer dog will be unpleasant and jealous towards other dogs. Rivals know to get into severe fight. This happens with foxes too. If equally strong dogs cross each other's path, the fight will occur immediately. During mating period, it is very intense in a wolf pack. Alpha male and alpha female must stay dominant over others making them sure that they will be the only ones mating. From the moment a male wolf mounts the female, mating can last for more than half an hour. When penetration is complete, the penis stays inside making the fertilization more possible. At this point, canids often stay "knotted" for couple of minutes. After the deed, the pack will relax. Cubs are usually born in spring, when it is warmer and food is more available. Few days before giving birth, female wolf will stay in the den, pulling hair from her stomach with her teeth, revealing the nipples.