Shelter puppy with one light blue and one darker colored eye
Everyone knows about ‘puppy dog eyes’ – that devious tactic which, if executed properly, can get certain members of the animal (and human) kingdom almost anything they desire. Who could resist, much less ignore, that oh-so-innocent expression coupled with those sad, gentle eyes? ‘I want,’ they say. And more often that not, they get.
Now imagine those very same puppy dog eyes were different in color from each other. Imagine the magnetic – nay, irresistible – effect two such dissimilar looking peepers might exert. These images of dogs with exactly this condition – known as heterochromia – will make you see puppy dog eyes to the power of two, and we’re sure the effect will be to elicit more than a few besotted ‘awws’.
A happy odd-eyed dog
Heterochromia refers to a difference in coloring in a person or animal’s eyes, hair or skin. Our focus will be the different colorations of the eye – or better, the iris, which explains why the condition is referred to as heterochromia iridum or heterochromia iridis. Heterochromia in animals is common among some species, where it tends to involve one blue eye; heterochromia in cats, for example, is fairly well known. It’s rarer to see people with heterochromia, but there are a quite a few famous examples of individuals affected, among them Dan Aykroyd, Mila Kunis, Kiefer Sutherland and even Alexander the Great!
Collie cross sisters with heterochromia
Although heterochromia is often associated with David Bowie because of the appearance of the singer’s eyes, according to some sources Bowie doesn’t actually have heterochromia. Instead, it’s thought he suffers from a permanently enlarged pupil – the result of an injury sustained during a fight that has made one eye look darker than the other. Bowie may not be a good example of an individual with heterochromia since his eye has not changed in color due to an uneven distribution of pigment in the irises – as is the case with these pooches.
The adorable collie cross sisters pictured have both got heterochromia, although it’s affected each in opposite ways – changing the right eye color of one and the left eye color of the other. It’s not surprising to see siblings with heterochromia because the condition is often inherited. In such cases, it’s generally passed on in autosomal dominant fashion, meaning that even if only one parent is affected, there’s a good chance the offspring will inherit the trait too.
With one light blue and one light brown eye, Mary Jane here is a real charmer.
In dogs, complete heterochromia is not uncommon. Complete heterochromia is said to occur when the iris of one eye is a different color than the other, and in man’s best friend it nearly always occurs with one eye colored blue and the other an entirely different hue. Other manifestations of heterochromia include partial or sectoral heterochromia – in which part of one iris is a different color from the rest of it – and this is also believed to be fairly common among our canine companions too.
With the innocent look in his eyes, try saying no to Ty for anything!
This adorable puppy, named Ty, appears to exhibit both complete and sectoral heterochromia: his right eye is blue and his left eye is brown, making him ‘odd-eyed’; but in addition, the left eye has a blue spot in it, meaning that it’s partially heterochromic. Factor in this pup’s all-round cute factor, and you have a pooch that we’ll bet can get almost anything he wants!
Meet boxer, cattle dog and Staffordshire bull terrier mix Iris. She’s a real cutie!
We’ve mentioned complete and partial (or sectoral) heterochromia, but there’s at least one other type, too. When the different coloration occurs as a ring around the pupil (with the outer hue the true color of the iris) we speak of central heterochromia. So, with these classifications out of the way, let’s look at a few more doggies with multi-colored eyes and take a look at the underlying reasons for the condition.
Aroooo! Beautiful Siberian husky, Lazy
What causes different eye colors in animals and humans? One of the overriding factors is the pigment known as melanin – and, particularly when it comes to heterochromia, its excess or lack. If there’s hardly any melanin there, a dog will have blue eyes; if there’s a little bit present, the eyes are more likely to turn out green; and if there’s quite a lot there, a dog will have brown eyes. So the more melanin, the darker the eyes.
Another rescue dog with heterochromia. This one’s called Sandy.
This shortage or excess of melanin is, of course, particularly pronounced in the case of heterochromia, as either only one eye or part of one eye is affected. But what’s behind these differing levels of melanin? Well, in both dogs and people, there are various explanations: it can be brought about by genetics – heterochromia is commonly inherited – or due to external factors such as eye injuries or disease.
Here we go: puppy dog eyes!
In dogs, however, there’s also another connection – one between merle coats and heterochromia. Merle is a type of pattern (rather than color) on a dog’s coat, and although it can occur in coats of all colors, it’s often seen in those that are brown or black. Other than changing the base color of a dog’s coat, merle also affects the coloration of dogs’ noses, paw pads, and eyes. And yes – you guessed it – the merle gene does this by altering the amount of melanin, so that part or all of an eye turns blue. This dog looks like it might be merle patterned, as do some of the others pictured here.
Hello there! Someone’s all bright eyed and bushy-tailed!
While many dogs are unaffected by the merle pattern and associated effects such as heterochromia, there is a connection between the merle gene and congenital deafness. Among merle dogs, the likeliness of being born deaf increases – and if two dogs with the merle gene have puppies, the risk increases even more.
Whatchoo looking at? Border collie with heterochromia
As well as making it more likely that a dog will have blue coloration in their eyes, the presence of merle genes also causes some dogs to suffer other eye defects. These include colobomas, or holes in the eye, and microphtalmia, a mutation that causes one eye to be unusually small. Although blindness is also associated, it has not yet been proven that the merle gene affects the eyes to the extent of causing a loss of sight.
One happy dog!
Stella, pictured here, is a harlequin Great Dane, so-called because of the white base coat color and irregular black patches covering the body. Grey patches are thought to be connected with merle markings in Great Danes but irrespective of whether or not her coat is merle, it’s clear Stella has heterochromia: one of her eyes has a dark pigment while the other is baby blue in color.
A husky cross with heterochromia
Though relatively rare in people, heterochromia is quite common in certain cat and dog breeds. Among canines, Siberian huskies are commonly affected; huskies, however, do not carry the merle trait, and neither does the Alaskan malamute, another breed known for the condition.
This cutie is not only a prime example of heterochromia iridum but also of the Catahoula bulldog breed, a cross between a Catahoula leopard dog and an American bulldog.
Other dog breeds in which heterochromia can frequently be found include Great Danes, Catahoula leopard dogs and Australian shepherds. Partial heterochromia is often seen in breeds such as border collies, Shetland sheepdogs, Welsh corgis, Pyrenean shepherds, mudis, dunkers, beaucerons, Catahoula curs, chihuahuas and dachshunds, all of which can exhibit the merle pattern.
This chipper-looking poodle has one blue and one brown eye plus sectoral heterochromia in one of the eyes.
We have to admit, the different types of heterochromia and what causes them can get a little bit confusing. But if your pooch has heterochromia, there’s no need to feel blue about their odd-colored eyes. If the condition wasn’t caused by trauma or illness, your heterochromic dog will see perfectly fine through both of its different-colored eyes. What can we say? ‘Vive la difference’!