Why Are Black Cats Black?

Though black cats make delightful pets, these felines have a spooky reputation. They have been called messengers of demons and servants of witches. It is said that if one crosses your path that you will be cursed with bad luck! These superstitions vary from place to place (In some cultures, black cats are considered lucky!), but the negative associations with black cats remain strong. While many people have heard scary stories about black cats, a lot fewer know the reason why they are black to begin with.

Photo by Joe Dzikiewicz

This melanistic black cat is grooming a young siamese cat. Siamese kittens are born entirely white. They have a mutated gene for producing melanin which only functions at low temperatures, giving adult siamese their classic color points.

Black cats are affected by a phenomenon known as melanism. Melanin is a pigment found in skin, hair, and feathers. Melanistic animals produce so much melanin that their color is blackened. Other famously melanistic felines include black leopards and jaguars (often just called “black panthers”), though different mutations cause melanism in each of the three felines mentioned so far.

Melanism does seem to pop up often in the animal world. Many other species across diverse groups have independently evolved melanism. Black variations of the gray squirrel are common in some areas (including at the Bruce Museum!). All black melanistic deer have been spotted in the wild, and there are melanistic zebras that look like their stripes are bleeding together. Melanism can also be found in reptiles, insects, and birds, including the rare melanistic black penguin.

This is a melanistic chinstrap penguin. Normal penguins of this species have white bellies.

So why might melanism be so common in the animal kingdom? There are a several answers to that question.

Photo by Malene Thyssen

These two snakes are European adders. One shows normal colors and the other is a melanistic variant.

At night, black animals are close to invisible. This helps prey species hide from predators, and helps predators remain unnoticed by potential prey. A rise in melanism can also help camouflage an animal in heavily polluted areas. The most famous example of this is the peppered moth in Manchester, England. During times of low pollution, the lighter form of the peppered moth was more common. When pollution caused darkening of the trees in the area, black melanistic peppered moths thrived.

The other benefits of melanism are less obvious. Research has shown that melanistic felines are more resistant to viral infection than their lighter counterparts. Populations with high numbers of black leopards may have been devastated by disease in earlier generations. This advantage helps explain why there are melanistic felines in places where they wouldn’t have much camouflage advantage.

Photo by Matthias Kabel

Melanism in jaguars is a dominant trait. If one parent of this cub was normal-colored, the other parent must have been melanistic.

So while black cats may seem sinister, remember that they are just one of many beautiful melanistic variations to have arisen in the animal world and may in fact be healthier than their lighter cat relatives. Maybe they’re not so unlucky after all! 

- Kate Dzikiewicz, Paul Griswold Howes Fellow