Normal Lengths of Time for Heat Cycles in Female Dogs

Once your female puppy is sexually mature and capable of reproducing, she'll begin routinely going into heat. This usually happens about two times every year in dogs. The heat cycle is characterized by telltale hormonal swings in pets. If you get your pooch spayed, however, she'll cease going into heat permanently.

Canine heat cycles generally last two to three weeks, indicates Vetwest Animal Hospitals. The exact lengths of heat cycles differ with every dog. While male dogs are drawn to females from the first days of their heat cycles, the females don't accept mating advances until a little time has passed. Female dogs are generally only open to mating with males for roughly half the time of the heat cycle, according to the ASPCA. They typically become fertile between nine and 16 days after the start of heat, when they begin to ovulate.

When female dogs in heat start to ovulate, they permit male dogs to breed with them, says Vetwest Animal Hospitals. They also often invite mating encounters at this time, with body postures that involve stiff hind limbs and raising their bottoms in males' directions. Females may attempt to break free from their homes, all in their tireless, hormone-fueled searches for male breeding partners. Some female dogs take it as far as diligently digging their own exit tunnels below gates in their owners' yards. The length of ovulation is approximately four days in female dogs, according to John Ross, author of "Dog Talk".

If you're not sure whether your dog is in heat, you might be able to tell by observing behaviors that are so typical of the cycle. Other key clues might be able to help you identify whether your pet is indeed in heat -- and keep track of how long the cycle is lasting, too. Dogs in heat usually seem especially heedful and attentive to their surroundings, according to ASPCA. They often seem more uneasy, wound up and irritable than normal, too. Physical signs also can be handy for figuring out if a dog is in heat. When heat cycles start, dogs usually experience swelling of their vulvae, says veterinarian Cheryl Yuill of VCA Animal Hospitals. The swelling is often subtle. Discharge with blood in it is also an indication. As heat progresses and female dogs become open to mating, the blood in the discharge diminishes.

It's impossible to guess exactly when a young female dog will start going into heat. Female dogs, for the most part, however, begin going into heat when they're between six months and two years of age. Large breeds usually mature later than those of smaller ones. If you want to ensure that your young pup never goes into estrus for even a day, consult your veterinarian about getting her spayed.