Why are orange cats mostly male? Scientists identify gene behind phenomenon

Every noticed how most orange cats are male, while females with some orange fur often have patchworks of different colors, such as the calico or tortoiseshell patterns.

“It’s been a genetic mystery, a conundrum,” says Greg Barsh, a geneticist at Stanford University.

Now, after decades of research, scientists have finally pinpointed the genetic reason behind this phenomenon.

Geneticists have discovered that the key to the orange fur coloration in cats is linked to a gene located on the X chromosome.

This gene, called Arhgap36, explains why orange cats are overwhelmingly male, while female cats with orange fur typically exhibit complex patterns, such as calico or tortoiseshell.

Genetics of orange fur

Male cats have only one X chromosome, which they inherit from their mother. Since the mutation responsible for orange fur is located on the X chromosome, male cats with the mutation will develop orange fur. In fact, most orange cats are male because they only need one copy of the mutated gene to express the orange coloration.

Female cats, however, inherit two X chromosomes—one from each parent. If one X chromosome carries the orange gene and the other does not, the result is a calico or tortoiseshell pattern, where different patches of fur may be orange, black, and white.

This happens because in female cats, one of the two X chromosomes in each cell is randomly inactivated, leading to a patchwork effect in fur color.

In rare cases, if a female cat inherits the orange mutation on both X chromosomes, she may also develop full orange fur, similar to male cats.

Discovery of the gene

After more than 60 years of research, two independent teams of scientists have identified Arhgap36 as the gene responsible for the orange coloration in domestic cats. The gene was found to be overexpressed in skin cells from orange cats, leading to the production of orange fur. This discovery confirms what many had suspected: the mutation that causes orange fur is located on the X chromosome.

Researchers have long known that the X chromosome plays a key role in fur color patterns, but it was only recently that scientists pinpointed the exact genetic cause of the orange coloration.

This breakthrough was made possible through genetic analysis of over 188 cats, including 145 orange cats, 6 calicos, and 37 non-orange cats.

Why does it matter? 

The discovery of Arhgap36 not only answers a longstanding genetic mystery but also sheds light on why orange cats are predominantly male. It also explains why female orange cats are rare and, when they do exist, often have a more complex color pattern.

In addition, the research has broader implications for understanding the genetic mechanisms behind coat coloration in animals. The mutation responsible for orange fur does not appear to have any negative impact on the health or behavior of the cats, debunking popular myths that orange cats are somehow less intelligent.

Link between fur colour and intelligence? 

Despite popular stereotypes about orange cats being less bright, there is no scientific evidence linking fur color with cognitive abilities. The overexpression of Arhgap36 in orange cats is localized to pigment cells, and it does not appear to affect brain function or intelligence.

This finding helps clarify the genetic basis for one of the most noticeable traits in domestic cats and provides valuable insights into how coat color patterns are inherited across generations.