The dog is an incredibly diverse species – from a two pound Chihuahua to a 200 pound Mastiff, there are hundreds of different breeds recognized worldwide. All of these dogs relate back to a common origin when they evolved from their wolf ancestors.
As a veterinary geneticist at Wisdom Health, I’m passionate about providing genetic insights to pet owners so that they can better care for their pets. I am particularly excited when we can utilize our data to discover new insights. My colleagues and I on the Wisdom Health team, along with researchers at Purdue University, have just published the most comprehensive study of dog coat color genes and physical traits ever completed covering nearly 12,000 purebred dogs from 212 breeds. We found that many breeds naturally carry unexpected traits and uncovered previously hidden relationships that may be found between breeds.
Please feel free to check out the study if you are interested in digging deeper into the science behind the findings, but in the meantime, here are some of my favorite fascinating tidbits about coat colors and other traits in dogs!
White spotting is so cool!
White spotting occurs when the pigment producing cells, melanocytes, do not cover a dog’s entire body so that areas lacking these cells stay white. While the puppy is still developing during pregnancy, the melanocytes start out along the center of the dog’s back and then spread down the body and from the back of the neck around to the face. Think of it like pouring a can of paint over a dog’s back and watching it cover most of the body but not quite reaching the toes, the center of the chest, the tip of the tail, or the middle of the face. That is how it works with melanocytes too!
If a dog has inherited one copy of the white spotting MITF gene variant, the typically have some white as I described on the feet, chest, face, and tip of the tail. If the dog has inherited two copies of this variant, then they often are mostly white with just some patches of color.
In our study, we found the white spotting variant most common in the sporting breeds like Pointers, Spaniels, and Setters and the Terrier breeds. Here is where the history part comes in – people have historically chosen dogs with white in their coats when they need to be able to see them better. This is particularly important for people who work with their dogs in heavy brush or vegetation to hunt or retrieve game and need to keep track of the dog.
Next time you see a dog with white spotting, think about where the pigment cells have migrated and how easy it is to find that dog at the park or in the dark!
Solid (colored) dogs are great too!
Ever tried to take a picture of an all black dog? It’s hard right? In contrast to their white-spotted counterparts, some breeds were meant to blend in and be inconspicuous. Some sporting breeds, like the Labrador and Golden Retrievers, historically sat quietly beside the hunter who did not want the game startled. Thus, having a dog with a solid or bland color would help the dog remain camouflaged blending into the surrounding vegetation until they were needed to retrieve the game. No surprise, we found that these breeds generally did not carry the white spotting gene variant.
Our study found that while most black dogs are related to a dominant gene variant (only requires one copy of the gene variant to show the trait), there is a second recessive gene variant (requires two copies to show the trait) that causes black which was previously only recognized in 6 breeds. However, it is surprisingly widespread across at least 89 breeds including the Weimaraner, Bulldog, and Pomeranian.
Next time you need to photograph your black dog, find a strongly contrasting background and ensure that there is a good light source to provide definition.
What about all white dogs then?
The ultimate in flashiness and visibility has to be the all white dog! Our data showed that several breeds that typically appear to have an all white coat such as the Bichon Frise, Maltese, West Highland White Terrier, and Samoyed are actually platinum blondes! Each of these breeds have a genetically yellow coat by carrying two copies of the MC1R gene variant for pheomelanin (the yellow pigment in the hair coat), however, they also appear to have a modifier gene that lightens that pigment to appear “platinum” or white. A recent study identified two such modifiers in cream-colored Australian Cattle Dogs and white Alaskan and Siberian Huskies specifically. Does that mean blondes really do have more fun?
A dog can also have a white coat due to a lack of melanocytes, the pigment producing cells in their skin. However, since these melanocytes are also required in the inner ear in order to hear properly, these dogs are often deaf in one or both ears. So this is one possible way to identify if an all white dog is a platinum blonde or lacks melanocytes all together – another way is testing with the WISDOM PANEL dog DNA test!
Unmask that dog!
Another fascinating finding in our study relates to the “mask” trait which produces a dark coat over the muzzle of the dog’s face as typically seen in breeds like the German Shepherd Dog and Boxer. This trait had identified in only 11 breeds previously, however, we found it to be present genetically in 164 breeds including the Dalmatian, Coton de Tulear, and Newfoundland.
Why such a difference? The mask trait is often concealed by other traits like a solid dark (black or brown) coat or by a dog with an all white coat making it impossible to see the mask over the face!
Can you hear me now?
One of the gene variants we examined in our study can impact whether the dog’s ears are perk or drop. Did you know that how a dog’s ears sit on their head is often related to the job they were bred to do? Dogs that need to be on alert and readily react to any little instruction like the herding breeds have big ears that stand straight up and help them hear everything going on all around them. On the other hand, dogs that were bred to work around loud noises like sporting breeds have drop or down ears that muffle the loud sounds protecting their ears from damage. They can also serve to keep dirt, seeds, and other materials out of the ears when working in brush or wet conditions.
The short but mighty!
Chrondrodysplasia is a big word for short legs! This trait, commonly seen in breeds like the Dachshund and Basset Hound, is due to genetic mutations that cause the growth plates in the long bones in the front and back legs to close early such that the dog does not reach their full height potential. This trait appears to date back to at least ancient Egypt and more recently was leveraged in hunting dogs that were short enough to chase their prey like badgers or rabbits down into holes or burrows. And despite their short legs, there are several versatile chondrodysplasic breeds that can herd cattle including the Cardigan Welsh Corgi, Pembroke Welsh Corgi, Swedish Vallhund, and Lancashire Heeler.
Who you callin’ Bob?
Dogs with a natural bobtail, often called a “stumpy” or “rumpy” depending on the length of their tail, generally share a single genetic variant in the T gene. Our study identified 48 breeds that carry this trait, 38 more than had previously been reported including the Boxer, Scottish Terrier, and Shih Tzu. Many of these newly identified breeds did not have obviously short tails so how could they have hidden this trait? This particular mutation can vary in the amount it alters the length of the tail and can even cause the tail to kink. Thus, a mildly shortened or bent tail may not be particularly note-worthy. In fact, many of the newly identified breeds allow shorter than average tail lengths, have naturally curled tails, and/or allow tail docking, all of which could mask small changes in length or structure of the tail.
Our understanding of canine genetics is always evolving which is one of the many reasons that this field is so exciting and fun to work in – we are always learning new, cool things! I also love sharing how the genes we study function to build our canine companions, so I hope you have enjoyed learning about the hidden stories in your dog’s genes.
One final shout out to all of you – these types of studies are possible because of the dedication of the WISDOM PANEL community who have tested over 1.5 million dogs with us globally – thank you!