My Grandpa litterbox trained is Chihuahua, simply because hawks and eagles are too much of a danger where he lives. Kasey (his Chi) was almost picked up by an eagle once and from that day on, they decided to litterbox train. It's worked very well for them. However, I don't believe it's necessary unless birds of prey are abundant in your area or there is some other kind of known danger. I have little dogs, and they go outside just as the big dogs do.