Photographers have been taking shots of incredibly rare animals with a condition that makes them appear much darker than the other members of their species. The condition is called melanism, and it is essentially the opposite of albenism, which makes hair and pigment whiter.
Some types of melanism are due to mutated genes, which is known as adaptive melanism because it is related to the process of adaptation. This is a natural form of melanism.
This happens because dark individuals become fitter to survive in certain environments, which makes them more likely to reproduce. This makes some species less visible to predators, especially during the night hours. Typically, adaptive melanism is heritable and passed down onto an animal’s young.
Adaptive melanism has been shown to occur in a variety of animals, including mammals such as squirrels, many felines and canids, and coral snakes. Adaptive melanism can lead to the creation of morphs, the most notable example being the peppered moth, whose evolutionary history in the United Kingdom is offered as a classic instructional tool for teaching the principles of natural selection.
Industrial melanism is an evolutionary effect in insects such as the peppered moth. Darker pigmented individuals are favored by natural selection, apparently because they are better camouflaged against polluted backgrounds. When pollution was later reduced, lighter forms regained the advantage and melanism became less frequent.
Melanism is found in many different species, including amphibians, reptiles, and mammals. The “black jaguar” was once thought to be a separate species but is now known to be a melanistic version of the same species, Panthera onca.
There are also other cases of altered pigmentation in addition to melanism. Erythrism is an abundance of red or orange coloration, while Xanthism is the abundance of yellow pigment and lack of other pigments. axanthism is the opposite, the absence of yellow pigment.