Chris Kaelin, a geneticist at Stanford Medicine, found himself thinking about cats. Not just any cats, but the loud, lovable, and often male ones streaked in unmistakable marmalade. These orange felines have baffled scientists for over a century, as about 80% of orange house cats are males. Why, among all mammals that come in sunset shades, are domestic cats the only ones whose orange coloring is so tightly bound to sex?
Kaelin now believes he has the answer.
In a 2025 study, Kaelin and colleagues report they’ve pinpointed the peculiar genetic mutation behind the orange coat in cats — and it’s unlike anything seen in any other mammal.
“For more than a century, orange coat color in cats has been recognized as an exception to the genetic rules that explain coloration in most mammals. Orange male cats are uniformly colored, but female cats often have a patchwork of orange and black fur, commonly referred to as tortoiseshell or calico patterns,” Kaelin told ZME Science.
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