I have a year and a half belgium malinois that I have had since a puppy, and is a extremely smart dog which has mastered all the obedience training without much effort. However, I am having such a hard time trying to teach him personal protection techniques. The problem is he has not learned that biting things and grabbing is a good thing. This problem has been an issue since he was a puppy, and I havn't figured out how to correct the issue.

While trying to make him bite and grab a 24 inch tug toy, he will simply just jump up and snap at it, while barely grasping it in his mouth. It is like he has no drive to even fight with it. Even with catch I can see this behavior, he will just run after a ball, pick it up in his mouth, then drop it. It seems like after the rush of getting the target is gone hes isn't interested in it anymore.

Any suggestions on how to correct this behavior?