You may have seen animals with two-colored eyes before. You may have even seen people with two-colored eyes. If so, you've seen heterochromia. What is heterochromia? It is an ancient Greek term that derives from héteros (different) and chróma (color). Heterochromia refers to a difference of color in the hair, iris, or skin due to an uneven distribution of melanin.
Heterochromia can be strikingly beautiful, but what causes it? While there have been many theories, scientists believe that most cases of heterochromia are caused by a lack of genetic diversity. A mutation in the gene that regulates melanin production only occurs when there is a chromosomal homogeneity. In most cases, heterochromia is genetically inherited, but there are some medical conditions that can cause it later in life.
Heterochromia can exist on its own, or as a symptom of a medical condition such as Duane syndrome. It is much more common in the animal kingdom than it is in humans. Similar to half-albino animals, animals with heterochromia boast at least two colors in their eyes or fur. It is especially common in white cats and Siberian huskies, but it can be seen also be seen in cattle, ferrets, and more. In almost all non-human animals, heterochromia involves at least one blue eye. Compiled below are amazing pictures of animals with heterochromia. Vote up the most fascinating ones!