Bobtail
Some dogs have a genetic disorder called “bobtail” where they are born without a tail or have a very short tail. This is caused by a mutation in the gene that regulates tail growth.
Bobtail dogs are born with a very short or no tail, this condition is seen in breeds such as the Australian Cattle dog, Australian Kelpie, and the Old English Sheepdog. The absence of a tail does not affect the dog’s health or quality of life.