Why kittens have blue eyes that change colour later

When faced with a very young, fluffy little kitten it can be hard to decide what is the most adorable thing about them, but one thing that most young kittens have in common are their large, bright and inquisitive clear blue eyes! However, much like human babies born with blue eyes who often develop a different colour as they get older, kittens’ eyes also typically change colour as they grow, meaning a blue-eyed kitten may well grow up to have green, amber or another colour-eyed coat.

If you have ever wondered why kittens are born with blue eyes that then change to another shade later on, this article provides a thorough explanation rooted in veterinary science. Read on to learn more about the fascinating process of eye colour development in cats.

Why Are Kittens Born with Blue Eyes?

Kittens are born with their eyes closed and usually begin to open them at around ten to fourteen days old. Their mother often helps by licking and grooming them, which aids the opening process. When the eyes first open, they generally appear blue. This is not because of blue pigment but rather an absence of pigment, specifically melanin, in the iris at this early developmental stage.

The blue you see is actually due to the way light scatters in the eye, specifically a phenomenon called Rayleigh scattering that reflects shorter blue wavelengths. At this point, the melanocytes, which produce the pigment melanin, have not yet become active in the iris.

Eye Colour Development as Kittens Grow

Starting around six to seven weeks of age, melanocytes in the iris begin producing melanin. The amount and distribution of this pigment then determine the eye's permanent colour. By around 12 to 16 weeks, most kittens have developed their adult eye colour, although in some cats, this may continue to darken for up to a year.

Cats can develop a wide range of eye colours including green, amber, brown, and yellow aside from the initial blue. Some cats display unique features such as flecks of colour or even heterochromia, where each eye has a different colour. This variation results from uneven pigment distribution during development.

Breed Differences and Blue Eyes in Adulthood

Certain breeds, such as the Siamese, are genetically predisposed to retain blue eyes for life due to specific DNA traits. Additionally, blue eyes are more common in white cats, which sometimes carry the trait that causes this permanent blue eye colour.

If your adult cat has blue eyes, it may indicate heritage from a breed that retains this trait. Knowing this can offer insights into your cat's origins and genetics.

Related Trait: Pigmentation and Health Considerations

Because pigmentation traits can be linked in DNA, blue eyes in cats are sometimes associated with other genetic features such as white fur and congenital deafness. For example, cats with one blue eye and white fur are more likely to be deaf on the same side as the blue eye. Understanding this link helps responsible owners to care for their pets thoughtfully.

When adopting or buying kittens or cats, it is important to source from reputable breeders or shelters that prioritise the health and welfare of the animal over appearance traits alone.

Conclusion

Kittens are born with blue eyes due to a lack of pigment in their irises. As they mature, melanin production defines their ultimate eye colour, usually by 12-16 weeks of age. Some cat breeds retain blue eyes into adulthood thanks to genetic factors. While eye colour is a fascinating aspect of feline development, responsible care and ethical breeding practices ensure your kitten grows into a healthy, happy adult cat.