male dog chasing spayed female..why?

I asked the question in the main board, but it might not be picked to be answered, so Im going to ask in the forum. I have 2 goldens. A male and female both 6 years old. I had the female spayed after her first heat. The male has not been fixed. Every so often, my male dog wont leave the female alone as if she is having a small heat. The lastest round is really annoying, as soon as she moves he is sniffing her and when she urinates he is right there. He tries to mount her, and follows her all around the yard with his nose right on her tail. This has been going on for about 3 weeks now. It's getting old and I dont understand why he is acting this way since she is spayed. She doesn't seem to mind all that much and she is healthy otherwise. Has anyone had this happen or do you have any ideas why he is acting this way?? Is there something I can spray on her to make him leave her alone? Why would he be so attracted to her urine? Thanks
i have two dogs female and male both female and male have been done but they are still doing it like rabbits not as much as they use to leave them to it and eventually he will start getting board
He hasn't been neutered..... some un-neutered dogs hump anything they can mount ! He's rampant and whether she's spayed or not, she's female.....