Instructions
Watch for signs your dog is coming into heat. A dog will have her first heat anywhere from six to 12 months old, and then at roughly six-month intervals after that. The signs can be behavioral as well as physical. A heat will typically last three weeks, during which time your dog will release pheremones that will attract intact male dogs. During this time, you must be very careful because dogs will dig under fences, break into outdoor pens and generally go to great lengths to get to a female in heat.
Watch for your dog's vulva to swell. Usually this is the first observable sign. It will be easier to see in short-haired dogs. Your dog will probably start spotting and leaving a bloody discharge. You will probably see her cleaning herself often, so watch for this, especially in longer-haired dogs. Often dogs in heat will urinate more frequently, and some may lose interest in food.
Be aware of behavioral changes, in both your dog and other dogs she is in contact with. While dogs in heat often become more affectionate and clingy, some become snappy and less tolerant of other dogs. If you have a multi-dog household, be aware that pack dynamics may change as your dog gets hormonal. It is best to keep your female crated or separated from other dogs, even spayed and neutered ones, in your absence.
Do not leave your dog outside unattended, even in a fenced yard. Intact male dogs can smell your female for up to a mile and will be very determined to get to her. It takes just a few minutes for an accidental mating. If your dog is small and a large or aggressive dog gets to her, it could be a traumatic and possibly harmful experience for your dog.
Be vigilant if you have an intact male in your household. Do not leave your female and your male alone unattended for even a minute, even if you think she is not ready to be bred. While ovulation usually happens during the second week, it is possible for a female to be bred in the first or third weeks. Your male may be distracted and off his food during this time so pay extra attention.
Buy some doggie underpants for the spotting if your dog is leaving a discharge on furniture or non-washable surfaces. Dogs vary in the amount of discharge they have and the length of time they will spot, but it can get messy. Bloody discharge may be present for just a few days, or for over a week. This will turn straw-colored during the second week when your dog is ovulating. Most pet stores sell disposable underpants and most dogs tolerate these well, although some will try to get them off to clean themselves.
Avoid walking your dog during the three weeks she is in heat. Every time she urinates, she will leave a pheremone calling card for male dogs, and most dogs in heat will urinate a lot to attract males. If you are in any type of dog classes, call first to find out the policy on having dogs in heat in class. You may have to miss a few weeks.
How to Manage a Dog in Heat
Unless you are planning to breed, your dog in heat should be kept away from males so she is not unintentionally bred or harassed. Whether you plan to breed eventually or not, no dog should be bred during her first heat because she is too physically and mentally immature. Some people feel it is best to allow a dog to mature sexually before spaying her, and this often means one has to manage a dog through a heat before spaying.