Can anyone advise on what constitutes a 'split heat'. My youngest girl had her first season at 9 months. She had her second season exactly 6 months to the day from the first. Based on that I expected her to have her 3rd roughly 6 months, maybe going towards 7 months. Her 6 months from the last is actually today.

6 weeks ago we were on holiday and during the week her behaviour changed (loopy doopy, tearing tissues, leaving little wee messages everywhere when out on walks) just the same as per her previous 2 seasons. She definitely appeared hormonal, but no sign of bleeding or swelling.

On the last day of holiday she was chasing around with my young male when suddenly he stopped playing, sniffed her rear end, mounted and the cheeky girl let him flagging her tail. No penetration took place as he was way off the mark and also I intervened but he was no longer interested anyway.

For the following week he found her extremely attractive first thing in the early morning, trying to mount her and she not objecting which is something she would normally do. This interest only lasted a week and only in the early morning after the first wee.

She is not showing any signs of comming into season at the moment and just wondering from any one who has experienced a split heat before (I have'nt) if it is possible without bleeding or swelling or possibly could it have been a very short dry season? On her first 2 seasons she bled like there had been a masacre but she has a small vulva and did not swell significantly.

I would be checking for signs of infection if the first wee is turning your boy on.  The first wee is always the strongest and it could just be that now she is fully mature, and if your boy hasn't been used at stud, he finds the scent irresistible (a seasoned stud would probably not be so interested ).  If her wee pattern is back to normal now I would not worry.

I have never experience a split heat either so hopefully someone will come along soon with the answer ;-)

Split heats occur when a bitch grows follicles on her ovaries and experiences the signs of pro-oestrus (swollen vulva, vulvar bleeding, attractiveness to males) but does not progress into oestrus and does not ovulate. The bitch's follicles will usually regress, and then she will come into a complete heat cycle with ovulation anywhere from two to 12 weeks later. Split heats are most common in a young bitch, especially at her first season, and are not considered to be associated with infertility when bred on the cycle in which ovulation occurs. Split heats must be differentiated from short inter-oestrous intervals between two true heat cycles. A vaginal smear will show red blood cells and intermediate and superficial cells as would be expected during pro-oestrus but in a split heat will not progress into an oestrus smear.

From a vet site so now I know what it is to ;-)