Sperm Can Live for Seven Days

Sperm can live for seven days in the female's genital tract. As a result, pregnancy almost always follows.

After a bitch has been in estrus, a unique sequence of events has evolved, which is different from all other domesticated species.

Her hormonal system "assumes" that she will be pregnant each and every time she comes into season, regardless of mating.

Even when not successfully mated, a female will still experience the full hormonal effects of pregnancy, with all the attendant physical and mental changes.

In pet dogs that have not been mated, the hormonal changes associated with estrus create a "false" pregnancy. In this condition, the female goes through the hormonal and sometimes the physical changes of pregnancy.

For some dogs, this even includes a degree of mild labor two months later. During her false pregnancy, a female can experience a dramatic variety of mood and sensory changes.

These include rejecting her regular food, making a den, and mothering objects such as toys. The most obvious consequence of a false pregnancy is milk production.

Some behaviorists believe that this milk production evolved so that these female pack members could supplement the nutrition of pups born to higher-ranking females.