When you are fostering a mixed breed dog everyone always wants to know what breed it is. As a rescuer, most of us know there is no real way of knowing what breeds your dog might be unless you run a DNA test. And in rescue there is no money or time for a DNA test. We try our best to give a good guess.
One of my adopted mixed breed rescue dogs has a shortened tail and so does one of my foster dogs. Of my owned dog, my vet isn't sure if it is a bob tail or if it was docked. However he is leaning toward bobbed. This can give a clue to her breed.
What is the difference? A dog is born with a bob tail. Tails are docked or cut off when the dogs are pups on some breeds for aesthetic and breed conformity purposes. Some believe that hunting breeds' tails are docked so they don't "break" while out in the field by getting caught on brush.
Pay attention also to where the tail is on the body and how they cary it. This can also gives clues to the dogs parentage.
Any dog can be born with a bob tail as a result of a genetic mutation. However there are some breeds that the bob tail is the norm and some that cary the bob tail gene and it is expressed frequently. Here is a list of some of them:
Australian Stumpy Tail Cattle Dog
Braque du Bourbonnais
Pembroke Welsh Corgi
Polish Lowland Sheepdog
Spanish Water Dog