Pigs’ tails
Why do domestic pigs have curly tails?
Picture a pig and your image probably includes a cute, curly tail. In the animal kingdom tails are used for balance, communication and many other purposes, but the purpose of curly pig tails isn’t easy to root out. In fact, pigs often fight by biting each other’s tails, so one theory is that they have evolved to be curly as this makes them harder to grab hold of. However, not all pigs have curly tails; wild boars and several other pig breeds have straightened tails, so it isn’t clear why the evolution theory would apply to some breeds of pig and not to others.
Another explanation is that domestic pigs have been bred by farmers for hundreds of years. While breeding for characteristics that are helpful on the farm, such as docility, farmers may have also bred pigs with curly tails, if these traits are inherited together by coincidence. Among some breeds a curly tail is thought to indicate that a pig is happy and healthy, while a straightened tail is a sign of stress.