As far as I know, it is how the dogs communicate with each other. All dogs have anal sacs back there and it is their personal scent. When they smell the scent, they know who the dog is and if it is friend or foe, male or female, alpha or submissive.
__________________ Diana-Mommy to Tessa  ,Harley ,Misty  & Boca    Post unto others as you would have others post unto you |