UTAH (ABC4) — Researchers from around the globe, including one from Utah State University, believe wolves in North America, especially those in the Rocky Mountains, may be selectively mating with other wolves based on their fur color.

It’s not a matter of vanity but rather of increasing a pack’s immunity against viruses.   

For decades, researchers from across the world have been studying wolves in the Rocky Mountains, particularly those in Yellowstone National Park. One of those researchers is Dan MacNulty, an associate professor in the department of wildland resources at Utah State University.  

“Biologists and non-scientists have wondered, ‘Why is it that we have some wolves in North America that are black and some that are gray?,’” MacNulty said. “What is the explanation for it?”

Since 1995, MacNulty has been studying the wolves at Yellowstone in hopes of finding answers. He and the other researchers now believe to have found them.   

“In the case of wolves, what we found is that a black coat color is linked to a gene that also confers resistance to disease,” MacNulty explained. “In this case, [the disease is] canine distemper virus.”

MacNulty said the color of an animal’s coat or a bird’s feathers can often be an outward expression of the creature’s health.  

According to him, the gene responsible for wolves developing black coats is a mutation. It’s something unique to wolves in North America. For that reason, the discovery has drawn global attention.   

“What we find in Yellowstone, actually, is that most of the mated pairs are black and gray,” MacNulty said.

He explained that the wolves may be selectively mating based on their coat color because they’ve become aware that by pairing up in this way, their pups are more likely to be immune to the virus.  

Wolves have roamed North America for thousands of years, much longer than humans after they migrated across the Bering Strait. However, he explained that this mutation likely originated in domesticated dogs that made their way up from South America with their human companions. At some point in history, domesticated dogs and wolves mated, and the gene was passed.   

He explained that the wolf population in Yellowstone is currently pretty evenly split between black and gray wolves. Visitors may come across white wolves, but MacNulty said that these are elderly wolves that were once gray.   

“These findings, these results, this study would simply not have been possible without long-term scientific research that has been done in Yellowstone,” he said. He emphasized that this could not have been done without the cooperation of the national park system as well as all those who were involved in the research.