Why do dogs have tails? Dogs mainly use their tails to communicate. The tail can show surprise, curiosity, apprehension, joy, and many other things. If you pay attention to your dog in different situations, you’ll learn their body language quickly. Some dogs use their tail as built-in entertainment and others as they work. For instance, the tail can be used as a rudder when swimming – the tail muscles work to balance and steer. There is a condition called “dead tail” when the tail muscles are overextended, making the dog unable to move it at all. It isn’t common, but can happen when an untrained dog attempts a day of hard work or play. The tail recovers, but muscle ache is painful and your veterinarian may prescribe a dog-appropriate medication for a day or two. Never give your pet painkillers intended for humans as some of them can be quite toxic and even lethal to animals.