bad enough, but when it's someone's leg that your pup is lifting his leg on, it's even worse. fortunately you can train your dog out of this unusual habit, provided you identify the cause.
dogs communicate by smell and scent marking is a very effective way for a dog to tell other dogs that the area they're in is his territory. in the wild, this is fine, but in the domestic context, it is not appropriate. some dogs care more about marking their territory than others and will seek to mark frequently, especially when other dogs are about. in some cases, the dog will become so fixated on marking his territory, 