by Some American black bears in the western United States have developed have cinnamon colored fur. The new hue is likely due to a genetic variant similar to that which causes albinism in humans, a new study finds.
Researchers from the USA and Japan analyzed DNS Samples of 151 American black bears (Ursus americanus) in the United States and Canada and found that those living in western states like Nevada, Arizona, and Idaho sported reddish coats rather than the black fur for which the medium-sized bears are named.
The researchers identified a mutation known as R153C in a gene called tyrosinase-related protein 1 (TYRP1), causing a change in the pigmentation of the fur, making its fur the same color as a copper penny.
“TYRP1 is a known pigmentation gene en route in the precursor molecules that ultimately produces either eumelanin (black or brown pigment) or pheomelanin (red or yellow pigment). Emily Puckett (opens in new tab), the study’s lead author and assistant professor of biological sciences at the University of Memphis in Tennessee told Live Science. “What it does is change the amino acid sequence of this gene.”
This “cinnamon variant,” which Puckett calls “a young mutation,” emerged about 9,360 years ago, according to the study, and has gradually spread through the population.
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Black bears elsewhere in the United States, including along the Great Lakes and in the Northeast, are less likely to display red-colored fur because this young mutation “didn’t have enough time for natural migration,” Puckett said.
“Geography definitely plays a role,” she said. “Our demographic modeling suggested that the most likely location for the mutation to occur was somewhere in the western region, very likely the southwest. From there it spread through populations by gene flow.”
But even that is a slow process, as the majority of East Coast black bears still sport jet-black fur.
“The bears don’t come through the Great Plains,” Puckett said. “If they wanted to go east, they would have to go north into Canada via the Canadian [Prairies], around the Great Lakes and then drop back into the eastern populations. That would take a long time. We see it happening and moving [eastward]but it’s a process that takes time.”
The researchers also looked at whether the evolution of this gene in Western American black bears has anything to do with thermoregulation, a mechanism that helps mammals regulate their bodies temperaturesor competition with another cinnamon bear species: brown bears (Ursus arctos), also known as grizzly bears.
“Our modeling suggests that yes, [the gene is] Adaptable in some ways, but we’re not 100% sure what it’s adapted to,” Puckett said. “We tested both thermoregulation and competition with brown bears and neither were strongly assisted. Our new hypothesis is that it is a selective advantage mechanism.”
Interestingly, the variant resembles oculocutaneous albinism type 3 (OCA3), known in humans, which causes lighter colored hair skintwo hallmarks of albinism. In some cases, there may also be visual disturbances.
“What is fascinating is that the bears show no signs of vision problems,” Puckett said, “as it would be difficult for them to survive.”
The results were published in the journal on December 16 Current Biology (opens in new tab).
