The reason why a dog’s tail is furry is because the hair has different functions on different parts of the dog’s body. The hair on a dog's body and face mainly serves to keep warm, waterproof and protect the skin, while the hair on the tail has different functions. The hair on a dog's tail helps them maintain balance and flexibility, especially when dogs are running, turning, or jumping. They need accurate balance to maintain body stability.
In addition, a dog's tail can also be used to convey emotions and communicate information, such as happiness, Excited or scared etc. Therefore, the long hair on a dog’s tail can help them complete these tasks better. Different breeds of dogs also have different tail hair lengths and shapes, which are related to their origin, purpose and function.