Mythology is filled with lore about black cats and white cats. Depending on where you hear the tales, one is lucky and the other brings misfortune. Is there anything scientific about this? Of course not. In reality, whether a cat has a black coat, a white coat or anything in between is the result of the level of melanin in the cat’s hair. It creates a spectrum including melanism, albinism, and more!
Feature Photo Credit: Ryusuke via Flickr
What is Melanin?
Melanin is a chemical created by a cat’s body which affects the color of that cat’s skin, coat, eyes, and claws. Humans and other mammals create melanin as well. Melanin is created inside special skin cells called melanocytes. Melanocytes can vary in size and shape -even within the same cat. Melanin is the result of oxygen mixing with the amino acid tyrosine within the melanocytes. There are two basic types of melanin found in cats:
Eumelanin is responsible for creating black and brown colors. It is the most common type of melanin in cats and humans.
Pheomelanin creates the colors red and yellow. The element sulfur is a part of the chemical mixture that gives this type of melanin its yellow hue.
How does this determine a cat’s coloring? Genetic components found on a cat’s X chromosome hold the blueprints for the mixture of eumelanin and pheomelanin the cat produces and where on the body they appear. Certain colors and patterns are related to the cat’s sex since melanin is controlled by X chromosome traits. Environmental factors such as UV rays from the sun, temperature, and certain health conditions can determine the amount of melanin that any part of the body needs at any particular moment.
Beautiful coat colors are not the only purpose of melanin. When melanin is released from the melanocytes, it is carried into the cells of the outer layer of skin. Once in the cells, the melanin surrounds the nucleus in each cell and guards the DNA within the nucleus from the harmful UV rays of the sun. While protecting from the harmful rays, it also helps absorb warmth from the sun. As an added benefit, the melanin carried to the cat’s coat can create colors and patterns which give the cat the right kind of camouflage to hide and hunt in their environment.
Melanism in Cats
Melanism is a condition in which a cat’s genes for melanin creation are turned all the way on. Since they display the highest amount of melanin possible, these cats have completely black coats. It is surprisingly common among cats! The Cat Fancier Association permits all black cats in 22 of its registered cat breeds. In the wild, there are 11 species of cat with a melanistic variation (typically with yellow eyes). True melanism is not outwardly displayed in humans, though it has been found in human internal organs.
Science still hasn’t discovered a definite purpose for melanism in cats. One theory is that the all black color is a great camouflage for cats that live in certain environments or that hunt at twilight. Another theory is that there are benefits to the cat’s immune system tied to the genetic trait for melanism. However, no studies have been able to prove either theory. What is known is that there must be a biological benefit to melanism in cats or it wouldn’t be so common from generation to generation.
Cats with melanism can appear dark brown! Melanin production is affected by prolonged exposure to sunlight. If your black cat spends a lot of time laying in direct sunlight, his/her coat may lighten. When sun exposure is reduced again, the new hair growth will be dark black. A melanistic cat’s coat can also become lighter if the cat is fed a diet that is deficient in the amino acids tyrosine and phenylalanine .
Albinism in Cats
Albinism is the opposite of melanism. In a cat with albinism, all of the genes for melanin creation are turned off. This results in a cat that has a solid white coat and pale pink skin. Albinism is much more rare in cats than melanism.
An albino cat may have blue or pink eyes. Even in humans, blue eyes are the result of little to no melanin being present in the iris of the eye. It appears that a cat has pink eyes when you can see the reflection of the taptem (similar to a human’s retina) in back of the cat’s eye through the iris.
Deafness is a common problem among cats with albinism. All white cats with blue eyes are likely to be deaf in one or both ears. In all white cats with one blue eye and one eye of another color, it is not unusual for the cat to be deaf on the side with the blue eye. Studies suggest that the genes that control melanin also control fluid levels in the ear. When melanin is not present (albinism), the fluid in the ear is absent as well. This results in the ear canal collapsing, causing deafness.
More concerning than deafness, cats with albinism are more prone to skin cancer than other cats. On areas of the body with light amounts of hair (ears, nose, etc), their lack of melanin leaves their skin’s DNA open to damage by the UV rays of the sun. Skin cancer in these cats can be prevented by limiting their amount of direct sunlight exposure.
Believe It or Not
The gene in Siamese cats that results in the darkened color of the ears, legs, and tail (called point colors) is actually a version of albinism. This partial albinism in cats is affected by temperature – both the body temperature of the cat and the temperature of the environment.
First of all, the dark point colors appear on the parts of the cat’s body that are naturally the coolest. Second, the cooler the environment, the darker those point colors will appear. Finally, a Siamese cat that moves from a cool environment (like Michigan) to a warmer environment (like Florida), the point colors will lighten! The reverse is also true -moving from warm to cool, the point colors will darken.
Have you ever met an all black or all white cat?
Sources & Digging Deeper
- Depigmentation Disorders in Cats: Changing Skin Color – Dr. Mike Paul, DVM
- Albinism in the domestic cat (Felis catus) is associated with a tyrosinase (TYR) mutation – DL Imes et al.
- Congenital and Inherited Skin Disorders of Cats – Merck Manuals
- Black Cat Appreciation Day: Do You Know Your Melanistic Cats? – National Geographic
- Malaysian Mystery – National Wildlife Federation
- Melanin – Encyclopedia Britannica
- Human pigmentation genetics:the difference is only skin deep – Richard A. Sturm et al.