So, what are they? oddly enough, they can be any kind of big cat! They’re the result of a big cat, most commonly a leopard or jaguar, being born with Melanism, a genetic disorder which causes more dark-coloured skin or fur pigment, or melanin, to form.
It is also the opposite of being born an albino. Because of the genetics involved, a Jaguar born to one normal parent and one melanistic parent can still have spots, but with dark patches.
This is because the chromosome isn’t completely dominant. Jaguars aren’t the only animals that can experience melanism. Most mammals, including squirrels, guinea pigs, cats, snakes,dogs and moths, can develop the condition.
It is often seen as a positive adaptation and can often make the animal better suited to its environment. In fact, the peppered moth’s recent evolution is almost completely centered around melanism.