We live in military base housing, and when we moved in, mulch/wood chips were in the backyard. It didn't take long to find out that our lab loves chewing on them and bringing them in the house. We are trying to find something to replace the mulch with that he won't be able to chew up, or get choked on, but will still use the bathroom on. We've thought about decent size rocks, but not sure if he will use the bathroom on them. We've also thought about sand, but don't know if we want a huge liter box, and for it to be tracked back inside. Any opinions or ideas would be very helpful!