
It can depend on many things, such as the breed concerned and the lines behnd her. I have had my flatcoat bitches come in season for the first time as late as 14.5 months and others much younger at 7 months. The best thing to do is keep a watch out for it from 6 months. Bitches coming into season will often urinate more often much the same as dogs mark their territory. The bitch is letting any passing male know she will soon be in season.