Dogs are usually in heat for 21 days. Female dogs have a cyclic sexuality that is independent of season unlike most animals. As for the male dogs, they do not have any cycles and are always ready for intimacy like most males of any species including human beings. Female dogs have a cycle of six months on average meaning they can be in heat twice a year.
The heat cycle has three distinct stages. They include:
During this stage, one may notice some bleeding from the vulva of the dog. The bleeding can either be heavy or light. Therefore, it is important that if the bleeding is heavy then as the owner you need to consider purchasing dog panties or special sanitary dog napkins in order to get rid of the mess. The vulva will also swell and the dog may urinate more frequently. This stage may last about ten days and the owner might notice an increase in male dogs around the home who might try to breed with the female dog even though she would like no part of them. The dogs might even go to an extent of serenading the dog and the owner all through the night!
It is however important to note that this cycle depends solely on the size of the dog. This is due to the fact that larger dogs e.g. Great Dane develop at a slower rate than small dogs such as Chihuahuas.
This is the second stage of the heat cycle which begins during the tenth day after the start of bleeding. The blood at this stage begins to change color from a bright red color to a clear discharge. During this stage, the serenade will have finally paid off as the female dog will allow any/all of the male dogs to mount her. The breeding can last for 4-7 days and it is important to note that the dog can get pregnant with mixed litters.
If you are not ready to take care of the litter, then it is highly advised that you confine the dog to the house for the necessary period of time. However, as the owner you will have to keenly look after her as most dogs would do almost anything including trying to chew the front door down in order to get to the panting males camping on the other side of the door. If you are interested in letting your dog breed, you may notice her willingness to do so by the way she stands still and lifts her tail away whenever you scratch her in the area directly above her tail.
As for six month old female dogs who come to heat for the first time, it is advised that you do not allow any mating to occur since the dog may become pregnant yet they are not fully grown/mature. Immature pregnant dogs usually have complications during the pregnancy with the complications affecting both the mother and the puppies.
In this stage the dog is getting out of heat. The dog will be giving off the heat scent and the male dogs will still be at the doorstep trying to serenade her and trying to get her attention. During this time, she will want no part of the males and will snap at them or even growl if need be. This stage lasts for ten days and once it is over the dog will remain out of heat for the next 6-8 months.