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A melanistic the Eastern gray squirrel.

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Definition: The term melanism refers to an increase in the average amount of the dark pigmentation that is present in an organism. The elevated pigment levels give rise to a dark individual that has, for example, dark skin, feathers, scales, or fur.

The term melanism (or melanistic) is also used to describe the phenotype of an organism in which its pigmentation is fully expressed (its pigmentation is dark).

Melanism has been observed in a variety of animals including leopards, jaguars, squirrels, wolves, peppered moths. Melanism is often the result of a genetic mutation. In jaguars, melanism results from a dominant gene mutation while in leopards, melanism results from a recessive gene mutation.

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