A curved dog tail can mean a variety of things. It may be a sign that the dog is happy or relaxed, as a wagging tail often curves to one side or the other when your pooch is feeling content. Alternatively, it can also mean that the dog feels threatened or uncertain - in this case, the tail will tuck between their legs and curl up tightly against their body. In any case, observing your pet's behavior in more detail can help you determine whether they need additional care or some extra affection.