I agree that your dog probally does like his but to be scratched, however my moms, alustralian colie, sherperd mix, does the same thing and mostly it is because she likes to be scratched there, but she also gets dermontidice (not sure how to spell that lol) and she gets it there, so she lovesssss to be scratched there. I'm, sure thats not your case, but it always a possibility.