Why Do Some Dogs Have Heterochromia?

Some dogs have different-colored eyes (also known as heterochromia) because of their genetics. It’s more common in merle dogs and some spitz breeds.

Jan 4, 2024By Thalia Oosthuizen
why do some dogs have heterochromia

Before we can understand the why, we have to understand the what. What is heterochromia? Well, it’s the unique trait of one blue eye and one green. Or one green eye and one brown. Even one blue eye and one brown. Whatever the color combination, it’s a unique trait that we humans share with our furry friends. Can you believe it?

As you gaze into these mismatched eyes, you may find yourself wondering: “Why does this happen?”

A Genetic Mystery

Dog with Different Colored Eyes
Image Credit: Pexels

Just like us humans, a dog's eye color is also the result of an interplay of genes. Dogs inherit their eye color from their parents as well. Heterochromia is an intriguing genetic puzzle. But it’s not quite as complex as you may imagine. The production and distribution of melanin, the pigment responsible for eye color, determines eye color. The iris, which is the colored part of the eye, may have variations in the distribution of melatonin, and this then causes heterochromia.

Specific genes dictate the production of melanin and cause some dog breeds to have more prevalently different-colored eyes. Fascinating, isn’t it?

Heterochromia Is More Prevalent in Some Breeds

Siberian Husky with Heterochromia in Forest
Image Credit: Pexels

While this genetic trait can occur in various breeds, some feature it more than others. One such breed is the Siberian Husky. These dogs already have a striking look due to their blue eyes and distinctive facial markings, but this look is even more awe-inspiring in instances where heterochromia occurs.

Another hot spot for this genetic marble is the Australian Shepherd. This breed is known for its merle coat pattern, a trait that often extends to its eye color. More noteworthy examples are the Catahoula Leopard Dog and the much-loved Border Collie. Different-colored eyes are also common in spitz breed dogs.

Though these breeds all differ in demeanour and attitude, they do have one thing in common - they are reminders that the universe is a marvel, and Mother Nature is an artist.

The Merle Gene Connection

Husky with Heterochromia in Snow with Harness
Image Credit: Pexels

Now that we’re clear on the fact that heterochromia is caused by genetics, the question is, what gene? As a dog lover, you may know that the merle gene is renowned for creating captivating color patterns in the coats of dogs. But did you know that it is closely linked to heterochromia? This is the gene that is at the core of dogs having two different eye colors.

How does it work? Basically, the merle gene operates by introducing a pattern of diluted pigmentation in a dog’s coat. This dilution then creates the merle coat pattern, the irregular patches of lighter color dispersed against a darker background.

This diluted pigmentation extends to the eyes as well, causing them to be two different colors. It’s important to understand that the Merle gene doesn't directly cause heterochromia, but it can lead to variations in eye colors in a single dog.

Heterochromia: Health Implications

Dog with Two Eye Colours Standing in Snow
Image Credit: Unsplash

Though this phenomenon carries with it a certain aesthetic allure, it can also have some health implications that will need attention. The condition in itself is benign and not life-threatening to dogs, but it can, in some cases, be associated with deafness or problems with your dog’s eyesight.

It is of the utmost importance that dog owners who have a dog with heterochromia not only admire the visual appeal of the condition but also be vigilant about addressing any health concerns that come with it.

To this end, you must take your four-legged buddy for veterinary check-ups and only do business with ethical dog breeders. Being a responsible dog owner means ensuring a happy and healthy life for your friend with mismatched eyes.

Selective Breeding Practices: Ethical?

Brown and White Dog Standing on Grass
Image Credit: Unsplash

To breed or not to breed? The breeding of dogs has long since been a very controversial issue, with dog lovers falling solidly on either side of the camp. Intentional breeding for specific aesthetic traits, including heterochromia, raises some serious ethical concerns. We find ourselves asking: “Is this really good for the overall well-being of our canine friends?”

Though these dogs are beautiful, how much harm are breeders truly doing to the breed as a whole by simply breeding pups that are nice to look at? This is where responsible breeding practices must take center stage, and dog breeders need to strike a delicate balance between what is pleasing to look at and what is harmful to the dog.

After all, what good are two different-colored eyes if a dog can’t see?

Cultural Significance: Legends and Folklore

Brown and White Dog Sitting in Garden
Image Credit: Unsplash

Beyond the biology of heterochromia, this unique trait has found its way into the legends and folklore of many communities. Spanning various civilizations and time periods, the mismatched eyes of dogs have held a special place in the narratives of different cultures. They are symbols of mysticism and even foretellers of destiny.

Long ago, Egyptians thought of ancient dogs as guardians and guides to the afterlife. Dogs with mismatched eyes were seen to be even closer to the divine and were often associated with the god Anubis. He was the deity of the afterlife, and these heterochromatic dogs were said to be companions to the world beyond.

Similarly, the Native Americans believed that these dogs were spiritual guides. They were the bridge between the here and now and the afterlife and were sent to guide chosen individuals through their life journeys.

Whether you believe the folklore or not, you have to admit that these dogs are pretty special.

Living with Heterochromia: Practical Considerations

Older Dog Lying on Green Grass
Image Credit: Unsplash

As pet owners, we know that adding a furry friend to the family is a commitment, not for your lifetime but certainly for theirs. So, it is very important that you realize that having a heterochromatic dog is an added responsibility, and you need to be prepared.

There are day–to–day considerations that come with caring for dogs with this particular trait. It may mean additional veterinarian check-ups and keeping an eye out for any signs of vision and other common health issues.

Their eyes may be a striking visual and pleasing to look at, but at the end of the day, it’s about giving these dogs the best possible environment to live in and making sure that you give them the happiest and healthiest life possible.

Thalia Oosthuizen
By Thalia Oosthuizen

Thalia has been a freelance writer for over a decade and a dog (and animal) lover for over 30 years. She grew up on a farm where, at one stage, she had 15 dogs. She currently has one dog, Avery - an adorable pavement special with an extra toe on each foot, and two rescue cats - Boris and Mango. In her spare time, Thalia enjoys running, cycling, swimming, and reading