Some American black bears in the western US have evolved to have cinnamon-coloured fur. The new hue is likely due to a genetic variant similar to one that causes albinism in humans. Researchers from the US and Japan analysed DNA samples from 151 American black bears (Ursus americanus) across the US and Canada and found that those residing in western states such as Nevada, Arizona and Idaho were more likely to exhibit reddish coats than the black fur for which the medium-sized bears are named. They identified a mutation known as R153C in a gene called tyrosinase-related protein 1 (TYRP1) that causes an alteration in the coat’s pigmentation that makes its fur the same colour as a copper penny. “TYRP1 is a known pigmentation gene that ultimately produces either eumelanin, black or brown pigment, or pheomelanin, red or yellow pigment,” Emily Puckett, an assistant professor in biological sciences at the University of Memphis in Tennessee, said. “What it’s doing is changing the amino-acid sequence of that gene.” This ‘cinnamon variant’, which Puckett calls “a young mutation,” came about approximately 9,360 years ago and has gradually spread through the population.
Black bears elsewhere in the US, including along the Great Lakes and in the Northeast, are less likely to exhibit red-hued fur because this young mutation hasn’t had enough time for S natural migration. “Geography plays a part,” Puckett said. “Our demographic modelling identified that the most likely place where the mutation arose was somewhere in the western region, very likely in the Southwest. From there, it expanded through gene flow throughout populations.” But even that is a slow process, with the majority of black bears on the East Coast still sporting jet-black fur. “The bears don’t pass through the Great Plains,” Puckett said. “If they wanted to go east, they would have to go up north to Canada, across the Canadian Prairies, around the Great Lakes and then drop back down into the eastern populations. That would take a long time. We do see that it’s happening and is moving, but it’s a process that takes time.”