Our RB Tomas, used to mat on his hips as he got older. By twenty, the old guy just couldn't reach back there anymore. We took scissors (he was a short-hair) and clipped the mats out. I think as they age they lay on their sides more and move around less. That may be one of the reasons for the mats. I'm praying the Boo is okay and just needs a "personal groomer".