One of my dogs is just over a year old and when he is outside will eat anything that he can get. He spends most of his time inside with us, but when I let him out to go to the bathroom or get some exercise, he always ends up trying to eat something. I am constantly taking sticks and plants out of his mouth when he comes in. I've even seen him pull small branches off of plants to chew on. I'm worried that he will one day get a bowel obstruction from eating things he should not be eating. I don't want to limit his outside time because he really seems to love it, but I don't want to risk his health. How can I train him to not eat everything in sight?