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Why do cats have different-colored eyes

You may notice that some cats have different color eyes. This feature is also present in humans, but in our pets it is more pronounced and occurs more often.

Occasionally we come across cats whose eyes are of different colors. This is an innate feature called heterochromia. It can be of two types — sectoral or complete. Most often, the term heterochromia is used to describe color differences in the iris, but it can also be applied to variations in hair or skin color.

Why do cats’ eyes have different colors

Eye color, especially the color of the iris, is determined by the concentration and distribution of melanin. There are only 2 pigments in the irises of mammals — eumelanin and pheomelanin. The total concentration of these pigments, the ratio between them, variations in the distribution of pigment in the layers of the iris stroma and the effects of light scattering play an important role in determining eye color.

The main cause of heterochromia is the lack of genetic diversity, at least in domestic animals. This is due to a mutation in the genes that are responsible for the distribution of melanin. They are usually damaged due to the homogeneity of the chromosomes. In cats , this occurs in two cases:

  1. When there is a dominant white gene in the animal’s genome, which masks any other colored genes and makes the cat completely white. These are, for example, Turkish Van, Turkish Angora, Persian and Khao-Mani.
  2. When there is a white spotting gene in the genome, responsible for two-color and black-and-white color. This gene prevents the melanin pigment from entering one eye during intrauterine development, as a result of which one eye turns out to be blue in a cat, and one green, yellow or brown. For example, this color can be seen in Turkish vans, sphinxes and Japanese bobtails.

There are 2 types of heterochromia:

  • Full — the iris of one eye is completely different from the other in color.
  • Sectoral — when a part of one iris differs in color from the rest of the iris and its center. In these cases, we can see a ring or “spikes” of different colors coming from the pupil.

At the same time, heterochromia in cats does not appear immediately. Like some other newborn mammals, all kittens have blue eyes, which can change as they get older. Differences in the color of a kitten’s eyes may not be noticeable until you study them carefully — in such kittens, each eye has a different shade of blue. The color of one eye remains unchanged, while the other changes over several months — for example, from blue to green or yellow, or from green to blue or yellow.


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