I was reading a training book, and the author brought out a good point. Just wanted to pass it along.
He advises against using tennis balls, or any balls that compress. Reason being, that a lot of dogs like to chew and compress the ball in their mouths, and there's a chance that the ball could become lodged/stuck in the dogs mouth/throat, and cause it to choke.

That is a really scary situation to consider.
Also, I just wanted to note, that you shouldn't give a dog a ball that is so small, in comparison to the size of its mouth, that it could accidentally swallow or choke on it when playing.
Naturally, most of this is "common sense", but I still wanted to pass it along so we're all more aware.
Let's keep our dogs safe
