I'm not positive but my dog is a healthy dog(nothing wrong with him) and he does that too because he is just wiping his butt. Its kind of gross realty and we have to use a steam cleaner when ever he does it so we don't have stains all over the carpet.

Dogs have an anal gland on each side of the rectum. These glands fill up with fluid. Each time the dog defecates some of the fluid comes out and "marks" the stool. This is why dogs smell each others behinds and smell each others poop. It is one way how dogs get to know each … Read more