Black Wolves Got Their Color From Dogs

Black wolves dominate packs in North American forests, but white wolves are commoner in the treeless tundra

Wolf distribution map (Canis lupus). Red: former range; Green: current distribution

Black wolf

John James Audubon's illustration of a black wolf

"Although it happened by accident, black wolves are the first example of wolves being genetically engineered by people," said one of the study's authors, Marco Musiani, a wolf expert at the University of Calgary. "Domestication of dogs has led to dark-colored coats in wolves, which has proven to be a valuable trait for wolf populations as their arctic habitat shrinks," Musiani said. "It also shows that human activities can help enrich the genetic diversity of wild animal populations, which is a very unexpected finding."

Using genetic analysis of wolf populations from North America and Europe, the researchers traced the source of the dominant gene responsible for dark coat color in wolves to domesticated dogs and conclude the trait was passed to the wolf population, as well as to coyotes, by means of hybridization with domestic dogs. The transition could have taken place, they say, as recently as the arrival of European dogs in North America or as long as 14,000 years ago when humans migrated into North America across the Bering Strait.

Since then, black fur has become commonplace in wolf packs, perhaps because snow-covered northern environments are shrinking and darker coloring allows for greater stealth while hunting in areas without snow. While wolves can be found in colors ranging from white to gray to black, light-coloration is predominantly found in the arctic tundra where wolves prey on caribou. The researchers note that the relationship between coat color and habitat is often attributed to adaptation and natural selection, but they say this is the first example of a genetic modification that likely arose due to human selection becoming adaptive and selected for when back in nature.

"I have spent a lot of time in tree-line areas at the southern edge of the tundra and it has always surprised me that there are white wolves and black wolves but no gray wolves in these areas," Musiani said. "This work may provide an explanation: Wolf populations are quickly adapting to conditions with less snow by taking advantage of the human-created shortcut of black coloration."

With tundra habitat expected to decline in coming years due to northern expansion of boreal forests related to global warming, the researchers note that black coloration may also help wolves survive in a changing environment.