Why Some Dogs and Cats Have Two Different Colored Eyes: The Science and Stories Behind Heterochromia

Pigment quirks in furry companions fuse biology and folklore into captivating stares.

By Medha deb

Created on Sep 19, 2025

Pigment quirks in furry companions fuse biology and folklore into captivating stares.

Why Do Some Dogs and Cats Have Two Different Colored Eyes?

Thereâs something enchanting about looking into the eyes of a dog or cat and discovering that each eye is a completely different shade. This striking trait, commonly known as heterochromia, gives many pets a memorable, magical appearanceâand often raises questions both about its causes and whether it hints at anything special or worrisome about the animal’s health. In this article, we’ll explore why some dogs and cats have two different colored eyes, the breeds most likely to display this trait, the underlying science, and the fascinating myths and stories that surround it.

What Is Heterochromia?

Heterochromia is the medical term for a condition in which the two eyes (or even parts of the eyes) of an animal or person are different colors. While it can occur in humans, heterochromia is much more visible and common in certain dog and cat breeds. Not only is this trait stunning, but it has a rich scientific and cultural background.

Types of Heterochromia

This phenomenon manifests in several ways:

Complete Heterochromia (Heterochromia Iridis): Each eye is a completely different color, such as one blue eye and one brown eye.
Sectoral Heterochromia: A single eye contains segments, or sectors, of two different colorsâthis is sometimes called “partial heterochromia.”
Central Heterochromia: The iris contains a ring of color different from the rest of the iris, often radiating out from the pupil in a spiked or starburst pattern.

What Causes Heterochromia?

The core cause of heterochromia is a difference in the concentration or distribution of melanin, the pigment responsible for coloring the eyes, skin, and hair. The more melanin present, the darker the color of the iris; less melanin results in blue or lighter colors. This uneven melanin distribution can be hereditary (genetic) or acquired because of injury, disease, or other factors.

Genetics: The Primary Cause

Most cases of heterochromia in dogs and cats are genetic, meaning they are inherited from one or both parents and are often present from birth.
Genes linked to coat color often influence the likelihood of heterochromia. In dogs, the merle and piebald genes decrease pigmentation and are strongly correlated with differently colored eyes.
Certain genetic combinations (such as white fur near the head and eyes) increase the UV exposure of the iris, which can change or preserve distinctive pigmentation differences.
Some breeds are particularly prone because of their genetic makeup (more on this below).

Other Causes

Eye Injury or Trauma: Physical damage to the eye may alter pigmentation and result in acquired heterochromia.
Disease or Health Conditions: Conditions like uveitis (inflammation of the uvea) or glaucoma may lead to a change in eye color. In such cases, other symptoms such as redness, swelling, or discharge are usually present and require veterinary attention.
Age: Some animals develop heterochromia as they age, but most retain the colors they are born with unless affected by injury or disease.

Breeds Most Likely to Have Heterochromia

While any breedâor even mixed-breedâdog or cat can display heterochromia, some are far more likely to do so because of their genetic makeup. Here is a closer look at these breeds:

Dog Breeds Prone to Heterochromia

Siberian Huskies: Perhaps the most iconic heterochromic breed, Huskies are famous for having one blue and one brown eye. Heterochromia is often seen even in purebred lines.
Australian Shepherds: This energetic working breed is known for its variety of eye and coat colors, including full or sectoral heterochromia.
Dalmatians: Their distinctive spotted coats are sometimes paired with mismatched eyes, especially when white patches are prevalent near the face.
Australian Cattle Dogs: Also known as Blue Heelers, they can have sectoral or complete heterochromia, particularly in blue-coated variants.
Border Collies: The rare merle pattern in collies often comes with sectoral or fully mismatched eyes.
Shetland Sheepdogs: Some lines, especially the blue merles, exhibit one or both eyes with unique coloration.
Catahoula Leopard Dogs: Their mottled coats are frequently accompanied by “cracked glass” or “marbled” eyesâsectoral heterochromia is common.

Cat Breeds Prone to Heterochromia

Turkish Van: This breed is mythically associated with heterochromia, often sporting one amber and one blue eye.
Turkish Angora: All-white Angoras frequently display pronounced heterochromia.
Khao Manee: Known as the “Diamond Eye” cat in Thailand, Khao Manees are specifically prized for having odd-colored eyes.
Japanese Bobtail: Some individuals, especially those with white coats, show strikingly different eye colors.

Among cats, heterochromia is more common in white-furred individuals whose genes suppress pigmentation in one or both irises.

The Science Behind Heterochromia

To understand heterochromiaâs expression, we need to look at the genetics of pigmentation. Messenger molecules called melanocytes distribute pigment throughout the body. The higher the concentration in the iris, the darker the eye. Genetic variationsâeither inherited or mutatedâcan mean that one eye receives more pigment than the other or that pigment never reaches one of the eyes.

Some key genetic variants involved are:

The Merle Gene (M Locus): Can produce marbled coat coloration alongside mismatched eyes; particularly in Australian Shepherds and Shelties.
The Piebald Gene (S Locus): Reduces pigment generally, causing white patches over coat and sometimes in one eye, especially in dogs such as Dalmatians and Bull Terriers.
The Epistatic White Gene (W): In cats, suppresses all color, making them whiteâand more prone to heterochromia because pigment doesn’t reach one eye.

In animals, heterochromia is far more likely to be harmless and hereditary rather than triggered by health conditions. However, any sudden or recent change in eye color for an adult pet should always warrant a veterinarian consultation to rule out disease or trauma.

Is Heterochromia Dangerous? Health Implications

In the overwhelming majority of dogs and cats, especially in breeds prone to it, heterochromia doesnât signal any health problem. Itâs simply a genetic quirk: animals with different colored eyes are no more or less healthy than their littermates.

There are, however, some complications worth knowing about:

Certain genetic patterns (such as “double merle” in dogs) may lead to an increased risk of hearing or vision issues, particularly deafness.
Heterochromia triggered by injury, inflammation (e.g. uveitis), or disease may signal more serious problems and require veterinary examination.

Veterinarians generally recommend observing your pet for any additional symptoms like discharge, redness, swelling, or visual impairment, which could indicate an underlying disease.

Fascinating Myths and Stories About Heterochromia

Throughout history, animalsâand occasionally humansâwith heterochromia have been objects of myth and fascination, often believed to possess special powers or mystical connections.

In some Native American legends, dogs with two different colored eyes are said to be able to see both heaven and earth at the same time.
In Turkish legend, cats with odd eyes are thought to bring good luck and are sometimes revered as sacred animals.
Among Siberian Huskies, the “spirit eye” belief holds that the blue eye can see into the soul or spirit world, while the brown sees the physical world.

Today, pets with this trait often become internet stars due to their haunting, photogenic gaze.

The Beauty and Uniqueness of Heterochromic Pets

While heterochromia may seem unusual, for many pet lovers itâs simply another thing to love about their companions. Some even seek out animals with this trait for its visual appeal. In the animal adoption world, pets with two different colored eyes often catch attention quickly both for their rarity and beauty.

Here are a few quick facts about heterochromia that highlight its allure:

Not exclusive to any one species: Heterochromia is found in dogs, cats, horses, and humansâbut is most visually pronounced in pets.
Often associated with affectionate personalities: Thereâs no scientific link between eye color and temperament, but many owners feel that heterochromic pets are extra charming and expressive.
Usually harmless: When not the result of trauma or illness, heterochromia is a benign and natural genetic variation.

Heterochromia in Humans vs. Animals: How Common Is It?

Species	Prevalence	Most Common Context
Humans	Rare	Usually congenital (from birth) or rarely acquired; seldom seen outside of specific genetic disorders or trauma.
Dogs	Common in certain breeds	Frequently hereditary; strongly associated with coat color genes like merle and piebald.
Cats	Moderately common, especially in white or mostly white cats	Typically due to dominant white or white-spotting genes; most visible in Turkish Van, Turkish Angora, and Khao Manee by breed.

In summary, heterochromia is a benign, beautiful trait rooted in genetics, celebrated by many cultures and adored by animal lovers worldwide.

Frequently Asked Questions (FAQs)

Q: Does heterochromia affect a petâs eyesight?

A: In nearly all cases where heterochromia is genetic, a petâs vision is not affected. However, if eye color changes suddenly in adulthood, consult a veterinarian to rule out underlying health issues.

Q: Are there any special care steps for dogs or cats with heterochromia?

A: No additional care is needed for heterochromic pets versus others. However, observe for any signs of eye trauma, redness, lesions, or sudden color change, which may indicate a medical problem requiring treatment.

Q: Is heterochromia only inherited, or can it develop over time?

A: Heterochromia is most commonly inherited and present from birth, but it is possible for it to develop later in life due to injury or disease, in which case veterinary evaluation is recommended.

Q: Can cats and dogs with heterochromia be bred?

A: Yes, and their offspring may also display heterochromia, especially in breeds where it is common. But breeding practices should avoid encouraging genes linked to serious health issues such as deafness or vision loss.

Q: Why are blue eyes often involved in heterochromia?

A: Blue reflects the absence or low concentration of melanin in the irisâit occurs most where pigment fails to develop in one eye during development, resulting in mismatched colors.

Conclusion

Heterochromia in dogs and cats is an eye-catching phenomenon rooted in genetics, especially in specific breeds with piebald or merle patterns or white-dominant genes. While captivating and sometimes steeped in myth, it is almost always harmless. For pet owners, those mismatched eyes serve as a reminder of the amazing variety in the animal worldâand offer yet another reason to appreciate our four-legged friends.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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