The Two-Faced Chimera Cat

The chimera cat has possibly the most captivating look of all felines thanks to its two-colored coat. But what kind of a cat is a chimera cat exactly?

Chimera cats have two sets of DNA, caused when two embryos fuse together in the mother’s womb. Instead of two separate individuals, a mother gives birth to one chimera cat, who has its own type of DNA and the type from the second embryo – a chimera cat is its own fraternal twin.

Chimeras can be traced back to Greek mythology. The word chimera comes from the Greek Χίμαιρα, meaning “she-goat or monster.” Chimera is described in Homer’s “Iliad” as the fire-breathing creature with the head of the lion, the body of a goat, and the tail of a snake.

Modern-day chimeras, although extraordinary, are firmly grounded in science, and their existence can be explained by genetics.

In this article, we’ll cover what causes chimerism and how to tell whether you have a chimera cat.

What kind of a cat is a chimera?

A chimera cat is born with two sets of DNA, which happens as a result of a merger between two embryos inside the mother’s womb at the beginning stages of pregnancy. Chimerism causes two distinct types of colorings on the cat’s body and face. The split coloration is sometimes perfectly symmetrical, which is what makes chimeras so interesting.

How do I know if my cat is a chimera?

Although the color difference can be conspicuous in chimera cats, the split coloring doesn’t always happen. Traces of different colors could indicate chimerism, even if they’re not equally distributed across the body.

According to scientific research, a tortoiseshell coat color that consists of red and non-red hairs is the most obvious way to identify chimeras in male cats. The tortoiseshell coat color is characteristic of female cats and its occurrence in male cats is associated with chromosomal abnormalities, such as an additional copy of the X chromosome.

When you see a male cat distinctively marked with smears of orange and black, you can assume it has an extra X chromosome or the entire set of DNA including the X chromosome. With females, it’s hard to tell because they already have two X chromosomes, so the coat isn’t a sign of chimerism by default.

The only way to be absolutely sure you have a chimera cat is through genetic testing. This is done by taking a sample of skin from each side of the cat. If the results of the test confirms the presence of two types of DNA – you have a chimera. If you’re curious about your cats genetics read our article on “Cat DNA Tests.”

calico cat personality

Chimera cat traits and personality

Chimerism isn’t a type of breed, so there are no specific personality traits associated with it. Chimera cats have the same behavior as other cats, and they need the same care. Also, chimerism isn’t a characteristic of a particular breed, so any breed can produce chimera cats. For a guide to feline behavior check out our article on “Cat Behavior & Body Language.”

What causes chimerism?

Chimerism in cats is caused by the fusion of two embryos in the mother’s womb, so a cat ends up containing the cells from the other embryo, in addition to their own DNA. However, chimerism can also occur in humans.

There have been only 100 cases of human chimerism documented so far. There are several ways in which humans can become chimeras, including through organ transplantation, pregnancy, and the fusion of two embryos.

If a person has received an organ or bone marrow from a donor, they are chimeras as they received cells and DNA from another person and now have two sets of DNA.

During pregnancy, the mother-to-be and the baby exchange cells. Most of these cells die off, but few of them may linger around. In that case, a woman ends up having the DNA cells from her baby, too, which is called microchimerism.

If a woman is pregnant with twins and one embryo dies in the womb, the surviving embryo may absorb the cells of the other one and gain another set of DNA – this is known as the “vanishing-twin” phenomenon.

Is chimerism hereditary?

In people, the children of a human chimera aren’t automatically chimeras because their two sets of DNA don’t mix in a single sperm or egg cell. Each sperm or cell will only have one type of DNA, therefore the children will only get one type of DNA.

In extremely rare cases, it can happen that a chimera’s baby was also produced by the fusion of two embryos, which would result in them becoming a chimera as well. However, this scenario isn’t more likely for a parent chimera than it is for anyone else.

Is Venus the two-faced cat a chimera?

In 2012, a cat named Venus took the Internet and the world by storm with her astonishing look – one half of her face colored black with a yellow eye, and the other half colored orange with a blue eye.

Although her striking two-faced markings could be a sign of chimerism, the only way to be sure is to do genetic testing. The mysterious pattern could have appeared by chance, with black coloration activating on one side of her face, and orange coloration on the other.

As she developed in the womb, the two patches met in the middle, resulting in a scarily accurate straight line that separates two colors.

chimera cat dna

Are calico and tortoiseshell cats chimeras?

Not necessarily. Although the majority of tortoiseshell male cats are chimeras, as the different colored coat is a sign of an additional X chromosome, with females there’s no way to be sure without genetic testing.

Why do some chimera cats have different-colored eyes?

Chimera cats are likely to have different-colored eyes because of two sets of DNA, but even cats that aren’t chimeras can have eyes that don’t match – this condition is called heterochromia.

Cats with heterochromia typically have one iris (the colored part of the eye) blue, while the other can be green, brown, or yellow.

The iris lacks pigment, so all cats are born with eyes that seem blue. During the kittens’ first few weeks or months of life, melanin is distributed throughout the iris, which causes the eyes to change color. This process happens in both eyes in regular cats, but if the cat has heterochromia, melanin is only distributed in one iris, while the other one remains blue.

Cats can also have a single eye that has different colors, which is called sectoral heterochromia. In such cases, a single iris is colored differently (e.g. green and blue) because of the uneven distribution of melanin.

Do chimera cats have health problems?

Up to date, there has been no scientific evidence to show that chimera cats have specific health problems. Chimeras, just like any other cats, may suffer from common health issues associated with felines, such as  heartworm, hyperthyroidism, diabetes, UTI problems, upper-respiratory infections, FIV and worms.

Can chimera cats reproduce?

Chimera cats are likely to be infertile because the additional set of DNA they get links the trait for their color to infertility. A scientific study that involved three male tortoiseshell cats found that two of them that were fertile had standard XY chromosomes, while the third one had an additional X chromosome and was sterile.

Are chimera cats rare?

According to experts, chimera cats are not rare, as most male tortoiseshell cats are chimeras. However, chimeras with eerily precise split-color patterns are hard to find.

chimera cat calico

Where can I get a chimera cat?

Chimeras can be found at rescue centers, shelters, or even wandering the streets. But chimeras with distinctive two-faced markings are extremely rare and unlikely to be found in shelters or the streets, although you never know!

Key takeaways on chimera cats

Chimera cats have two sets of DNA which they receive during the fusion of embryos inside the womb. Their two halves of the body are colored differently, and the line that separates the colors can be incredibly straight as if done by hand. However, even cats with small pops of different colors can be chimeras.

Chimera cats aren’t as rare as people think, as most male tortoiseshell cats are chimeras. However, the only way to be sure you have a chimera is to have genetic testing.

Although chimeras could be found in animal shelters, rescue centers, and even in feral cat colonies, the ones with distinctive split coloration are rare. If you do get lucky to have one as your pet, you don’t have to worry about any specific care requirements – in that sense, they’re no different than any other cat.

Feature image credit by Irene Souto. 

Ana Markovic