Black Wolf Mystery Solved

The reason North American wolves have black coats may surprise you; scientists found it’s the result of historical matings between black dogs and gray wolves.

Gray wolves have that name because of their color, but in North America many of them have dark or black coats instead of the standard gray.

A team of researchers led by Gregory S. Barsh of Stanford University found a genetic mutation producing dark coats appears to have occurred in dogs, and then spread from them to wolves when the species mated.

The research, federally funded by the National Science Foundation, is published in the online edition of the journal Science.

Researchers discovered that dark-coated wolves are almost exclusive to North America and are common in forested areas where they make up 62 percent of the wolf population, compared with 7 percent in open tundra.

But wildlife biologists don’t think wolves rely much on camouflage, Barsh said. “It’s possible there is something else going on here.”

“It’s sort of intuitively appealing, when you see animals that sort of blend in with their environment, to say … that explains natural selection, that somehow they are better camouflaged either as predator or prey,” said Barsh.

However, he said wolves don’t have a lot of predators, and there’s no evidence a black coat color leads to any increase in a wolf’s ability to capture its prey.

The scientists used molecular genetic techniques to analyze DNA sequences from 150 wolves, about half of them black, in Yellowstone National Park, which covers parts of Wyoming, Montana and Idaho.

Researchers found that a mutated gene in dogs, known as the K locus, is responsible for black coat color.

The same protein responsible for coat color is associated with fighting inflammation and infection in humans.

Thus, it “might give black animals an advantage that is distinct from its effect on pigmentation,” Barsh said.

Researcher Tovi Anderson said humans have cultivated the mutation for black coats in the domestic dog for thousands of years.

“Now we see that it not only entered the wild population, but also is benefiting them,” she said.

Genetic tests show the mutation was introduced into wolves by dogs sometime in the last 10,000 to 15,000 years, Anderson said.

“We usually think of domestication as something that is carried out to benefit humans,” Barsh said. “So we were really surprised to find that domestic animals can serve as a genetic reservoir that can benefit the natural populations from which they were derived.”

“Although it happened by accident, black wolves are the first example of wolves being genetically engineered by people,” added co-author Marco Musiani of the University of Calgary in Canada.

“It is somewhat ironic that a trait that was created by humans may now prove to be beneficial for wolves as they deal with human-caused changes to their habitat.”

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