I believe that jester's mom's dog was peed on a time or two by going to sniff a spot that was already chosen by another. We laughed about it but I am sure it is a really irritating problem to have when it happens consistently. I have no idea what you can do to stop it other than to have them on leash as mentioned above and be able to pull him out of the way. I really don't believe that this would be done intentionally. I hope that someone has some good advice for you to help you out.