What is Natural Bob Tail in dogs?

Natural Bob Tail is a genetic mutation in some dogs that results in a naturally short tail. The length of the shortened tail varies between individuals from no tail at all to just a short version of what the tail would otherwise be. On its own, a bob tail poses no health concerns to the affected dog and if this is where any concern ends, Natural Bob Tail would not be a condition at all but simply a physical trait that may or may not be desirable in appearance. The problem Natural Bob Tail arises when a dog has two copies of the affected gene making it a fatal condition.

Genetics of Natural Bob Tail in dogs

Natural Bob Tail is an autosomal dominant trait, meaning that of the two copies of the T gene the dog inherits from it’s parents, if any one of the genes have the C189G mutation, the dog will have a bob tail. This is the nature of dominant mutations. Dogs with 2 normal copies of the gene will be unaffected by bob tail, dogs with 1 normal copy and 1 mutated copy will have a bob tail and dogs with 2 mutated copies will not survive long enough to be born. This is why 2 dogs with Natural Bob Tail should not be bred as about a quarter of all the puppies that are conceived will usually fail to live. Breeding a Natural Bob Tail with a normal dog will result in half of the litter being Natural Bob Tail. 2 normal dogs will not produce any puppies with Natural Bob Tail.

Severity of Natural Bob Tail in dogs

Dogs that are born with Natural Bob Tail will have no adverse side effects of their bob tail. However, puppies that have 2 copies of the mutated gene will usually not survive to be born. These puppies are usually reabsorbed into the mothers body very early in the pregnancy so the effect is a reduced litter size by about a quarter.

Diagnosis of Natural Bob Tail in dogs

Identifying dogs with genetic Natural Bob Tail is fairly straight forward in countries like Australia where tail docking (removing part to all of the tail in the first few days of life) is illegal, but imported dogs and those dogs that have been docked illegally are harder to identify as carriers. The only definitive way of knowing if a dog is Natural Bob Tail is to perform a DNA Disease Test to identify the mutated gene in the dog being assessed.

Natural Bob Tail Controversy

This condition has caused some controversy in the show breeding fraternity with some breeders of traditionally docked dogs who often display Natural Bob Tail such as Rottweilers and Corgis preferring dogs with the genetic mutation. Others see the reduced litter sizes as denying the unborn puppies a chance at life as well as reducing the numbers of dogs they breed. Depending on which side of the argument you believe is true will often colour what you see as a beneficial genetic mutation or one that removes otherwise healthy dogs from the breed population.

References

Hytönen et al (2008), “Ancestral T-Box mutation is present in many, but not all, short-tailed dog breeds”, Journal of Heredity, Advance Access published online on October 14, 2008
Haworth K, Putt W, Cattanach B, Breen M, Binns M, Lingaas F, Edwards YH. (2001) Canine homolog of the T-box transcription factor T; failure of the protein to bind to its DNA target leads to a short-tail phenotype. Mammalian Genome. 2001 Mar;12(3):212-8
Fantastic Account of Dr Bruce Cattanach’s Bobtail Boxers Virginia Zurflieh, boxerunderground.com, Oct 1998.