Short season?

Question
I have a five year old staffordshire bull terrier bitch.  We also now have an 18 month old dog.  She recently had what appeared to be the start of her season, and had some of the clear/pinkish discharge that she normally does.  Our dog showed a lot of interest in her and "mounted" her a lot but they did not appear to mate properly and we did not see them "locked" at any time.  Since that time she has not bled as she usually does, i.e.. there have not been the usual red spots on the floor where she sits or lays.  Has she successfully mated which caused her short season or is this short season a cause for concern?  She has never had a litter before

Answer
Hello Ian:

The fertile portion of the dog's heat cycle is when the vaginal discharge becomes less in both flow & color. This usually occurs about 9 to 10 days from the initial onset of the cycle, where you'll see the bloody vaginal discharge & swelling of the vulva. This is why so many unplanned pregnancies take place - many people think if their female is no longer bleeding all is safe. Try to count back to determine when her cycle first began. If it's been much longer than 9-10 days ago, she may be experiencing a split heat, where the cycle stops abruptly but will usually begin again within a month or more or less. It's certainly possible mating actually did occur when you weren't nearby or they may have achieved a pregnancy without a tie - some dogs manage this quite routinely. Unfortunately I can't give you any additional examples of the possibilities so you'll simply have to wait & see what time will tell.