There is hurdly anything that can stop Sarplaninac (or CO) to do what they are think it's right, especialy when defending their teritory. Strong, big metal fence would probably do the job, but even then they will try to dig under the fence or to jump over. But, don't worry, Sarplaninac is not the dog who like to wonder around, in their natural habitation they are set free all their life. Problem could occure when he smels the female that is in heat. Aleksa aleksatomic@yahoo.com