He did play with other dog.... he does pull when we walk him and we use a collar, I'm going to start using a harness instead.... and he does chase squirrels in the fenced in yard. I have seen his head turned quickly when he reached the fence. And one time my husband didn't know that he (the dog) was still in the yard and closed the porch door, and he (the dog) ran to the door to get in and hit his head once. So my point is that he could have sprained his neck while I wasn't with him.