When the anal glands are very full some pets will start scooting their rear ends on the floor.
In most cases scooting is caused because your dog has not been able to empty their anal glands (also called anal sacs). These glands are two small glands present on both sides of your pet's anus. These glands produce a thick fish-smelling discharge.
Some pets will empty their glands naturally during normal defecation and walking around but for some pets it's more difficult and someone has to empty it for them as it can become impacted and very uncomfortable, potentially leading to other complications such as infection or abscesses.