Ihave a sort of short sideways hole in my yard and I will be having a dog stay soon who will eat whatever the hole is for? Is there a way to discourage use of hole for future use - is this likely a rabbit den?

If you can see the bottom of the hole that's probably a rabbit then if you can't it could be anything from Chipmunks to groundhogs

Sorry, I don't know what type of animal home that is. The dog will likely win any animal confrontation. Doesn't sound like a skunk house, that would present a problem.