More and more black squirrels have been popping up across Michigan and in some other northern states and climates, and residents are taken aback by their unique color -- some have even mistaken them for rats with bushy tails. However, experts reassure that the animals are still gray squirrels; they just have a gene that expresses itself differently.

"Black squirrels were not very common except for in certain locations," Tim Payne, wildlife supervisor for the Department of Natural Resources, said in a statement. "Now, as I travel about... I see them in scattered areas."

While they are mainly found in northern states and climates, their mating spreads the gene for darker fur around. This is why they have been seen more regularly. 

Researchers say the dark pigment of their fur ultimately helps them retain heat -  a benefit during Michigan's frigid winters -  but can also make them easy prey due to their contrast against white snow.

Eastern gray squirrels -- including the black-colored ones -- are most common in heavily forested areas, says John Koprowski, a professor at the University of Arizona who has studied squirrels for decades.

He also pointed out that squirrels are often seen in our yards because houses built in the suburbs 50 to 60 years ago are now surrounded by matured trees that resemble the forest.

The eastern gray squirrel can be seen throughout the U.S., from Florida to Canada and from areas along East Coast to areas out west. However, the black variety is more common the farther north you go.

The Black Squirrel Project is part of an ongoing study in the United Kingdom, too. 

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