THAT IS TERRIBLE!! the dog is just doing what it does best, protect its turf. The ammonia could really harm the dog if it not diluted enough, get the halt its like 7$ or an air horn. Ive found that just yelling at the dog often confuses them, giving me enough time to take off ahead. I have a friend in PA that makes his own anti dog spray out of a little chili powder and water, just enough to irritate the dog but with no intent on harming it.