A dog is “in heat” or “in season” when she is in estrus. This is the veterinary term for the point in a female dog’s cycle when her body is producing hormones that make her attractive to male dogs. During this time she is becoming able to mate. A female dog, which is correctly called a bitch, usually stays in heat between about four and 25 days. However, the exact time that your dog may be in heat can vary from dog to dog.
The Estrus Cycle
Female dogs can have their first heat when they are around six months old in some small breeds. Most dogs will have their first heat by the time they are around 12 months of age. However, larger dogs may not have their first heat cycle until they are 14 months of age or older. It is not unusual for some breeds to have their first heat cycle when they are 18 months old or older.
The heat cycle has four stages:
is the first stage. When your dog is in proestrus she will have a vaginal discharge that is bloody at first. This is when the owner first notices that something is different. The discharge will gradually change to a clear or pink-yellow discharge over the next several days. As the discharge becomes clearer, the dog is getting closer to being ready to mate. Males are attracted to the female dog at this time though the female dog is not willing to mate for several more days. Pregnancy does not usually occur until the female dog is willing to mate and the discharge is clear or yellow.
stage the dog’s vulva will become soft and swollen. The vaginal discharge will be yellow. This is the time when mating can occur. This stage may last for several days or for just a day or two. Some female dogs will only accept a male dog for a day or two and then they will snap at a male dog who tries to mate.
is the time period following estrus or following the dog’s mating. This period lasts between two and three months. If your dog is pregnant she will be eating more and her body will be preparing for the birth of a litter. Even if she is not pregnant, her body will go through some hormonal changes before returning to a more settled period.
is the inactive period that follows diestrus. The female dog is sexually inactive during this time and the hormones are more settled. This period lasts until the next proestrus phase begins again. This can be two or three months or, for some dogs, it can be up to a year before the next heat cycle.
Frequency of Heat Cycles
Unfortunately, there is much misinformation on the Internet about heat cycles and most people believe that dogs have a heat cycle every six months. This is not true, especially for larger dogs. Many, perhaps even most dogs, only have one heat cycle per year, especially larger dogs. It is not unusual for a dog to go nine months or more between heat cycles. Many large breeds may go a year between heat cycles. Much of the information on the Internet seems to be based on what is normal for Toy breeds which is not normal for other dogs.
Every dog owner need to have at least one good reference guide to their dog’s health. If you haven’t got one already, make sure you get one now. The guide that I recommend is called The Ultimate Guide to Dog Health shoot on over and grab yourself a copy and save your canine friend any unnecessary pain and not to mention save a fortune on avoidable health care costs.