We had a perfectly trained 18 month old great dane... until we brought home the boston terrier puppy. Heffy, the dane, is a digger, so we gave her a specific place in the yard to go at it. We even have a way to close it off and she wouldn't dig at all if her "sandbox" wasn't available. Now Heffy and Gimlet are both digging in some other spots in the yard. They almost always do this when we are not home, so it is hard to correct them and redirect to the appropriate digging spot. We've tried putting poop in the holes and they just dig it up. Any suggestions?