I have noticed something very interesting with my 3 month puppy. I am busy training him to retrieve an article. As young puppies go he will sometimes chase after the ball with great enthusiasm but then fail to bring it back to me and rather lie down and chew on his prize. I then did a bit of trouble shooting and tried to exchange the ball for food once he retrieved it. The problem with this is that once the food came out his prey drive diminished significantly. I then devised another plan where I would first play tug-of-war with one of his favourite toys to stimulate his prey drive and once he is as crazy as a Malinois with drive, throw the ball and then use the tug toy as a reward for this behaviour once he retrieves the article. So far this is working like a dream. What I then do at the very end of the training session is to give him a food reward as well. In the dog's mind this is like simulating a hunt. I am a firm believer of working WITH nature to get the best behaviour out of my dog. Could it be that once you introduce food, the prey drive gets diminished because in the dog's mind the need for prey drive is no longer needed because food is presented?