Dogs in heat

Female dogs are "in heat" when they have entered the fertile part of their reproductive cycle. A heat lasts for 3 weeks on average and a dog will usually go into heat every 6 to 8 months.

Most breeds have their first heat at about 6 months old but it may be earlier or later.

A heat can usually be identified when there is some bleeding from the vagina, a swollen vulva or increased urination. Female dogs do not produce very much blood however, and in a small dog you may not even notice the bleeding.

Unwanted attention

The first thing you will notice if you have a bitch in heat is that she will attract un-castrated male dogs within a very large radius. Her behaviour will change too, so while she normally wouldn't let males mount her, she almost definitely will while in heat.

Additionally, male dogs will go to surprising lengths to get to a female in heat. While your bitch is in heat it's inadvisable to leave her unsupervised outside, and you'll need to keep her on the lead at all times while on walks. In general, other pet owners you encounter will be able to control their dogs, but the scent of a female in heat can cause aggressive behaviour in some dogs.