Just when does it occur?
As I was caught in surprise about what is happening to my dog, I came across looking for answers about this. Well, for starters a female dog may start to be in heat when she is about 6-12 months. This is because at this stage she may start to have her first estrous cycle. Although this is not always the case for all dogs as some larger dogs may start to have estrous during 12-24 months of their lives.
I noticed also that my dogs are bleeding much similar to a female human being. It may take about 2 weeks or so before being “in heat” subsides.
Tell tale signs
A female dog in heat may be recognized by the bleeding of her vagina. Also you will notice that the vulva is swelling. Aside from this, if you try to press her back, she may instinctively raise her tail in anticipation of a male dog embarking. You might have a little problem for small dogs as it is not easy to spot whether she is in heat or not.
During this period, female dogs can become pregnant that is why if you want to breed your dog always do it during her estrous days. In this manner, you increase the chance of her getting pregnant.
But whatever you want with your dog, always take care of your her and never forced her to mate just so you can have her litters. Just remember a dog is a loyal and sensitive pet.