There are a few reasons why a dog could be scooting his butt across the floor. The first and most simply reason is that he could just have an itch that he can’t get to any other way. Dogs that have an itch will only scoot their butts every once in a while.
Another reason that a dog could scoot his butt would be tapeworms. Tapeworms come out of the anus when a dog defecates and could get stick around the anus. These tiny parasites could be very bothersome and itchy to dogs, who will relieve the itching by scooting their butts across the floor.
A dog could also have anal glands that are full, which causes discomfort. Anal glands need to be expressed once they become full. Most dogs will lick their anal area and be able to keep the anal glands empty, but some dogs don’t do this or aren’t able. Full anal glands will look like tiny lumps around your dog’s anus, and he may scoot his butt in an attempt to empty the anal glands or get relief from the pain.