The Tail Chakra in dogs acts as an extension of the Root Chakra in many ways. It provides additional grounding and a feeling of security. It also connects to the Throat Chakra to provide more open communication channels. Dogs share a lot of information via their tails.
What about dogs who don't have tails you may ask? They wiggle that entire area (yep, wiggle butts). In my opinion, the lack of a tail does put dogs at a disadvantage. Other dogs cannot read signals from them as easily and may misinterpret their motives. Have you seen a dog walking toward another dog with that high, stiff wagging tail...pulled up really tall? That is an "I am friendly, but if you act snarky, I will turn Cujo on you."