(Lucas, TX, United States)
My year and a half old Jack Russel Terrier has a chicken chasing problem. He is submissive and will not chase them when I am around, but has already killed one chicken that got into his pen when I was not there. He also loves to chase cows and horses, even though he has been knocked silly several times. He was not introduced to those animals during his puppy months, so I believe it may be too late. Is there anything that I can do to train him to stop his terrible habits? Or is that just an instinct that I was too late in stopping?