Study finds no domestic dogs in Mexican wolf lineage

Controversy has surrounded the reintroduction of Mexican gray wolves (Canis lupus baileyi) into the mountains of Arizona and New Mexico, including questions about the purity of their genetics. Are these truly wolves, some skeptics have wondered, or are they hybrids with domestic dogs?

Previous genetic techniques have found almost no shared genetics with domestic dogs, but genomic technology has evolved in recent years, giving scientists better tools to look more closely than ever before.

“This is an issue that keeps getting thrown around,” said Robert Fitak, lead author on a study published in the Journal of Heredity that used modern genomics to examine wolf ancestry.

Once widespread in the mountains of the Southwest, the Mexican gray wolf was brought to the brink of extinction by predator removal campaigns in the early 20th century. To begin reintroduction efforts in 1998, three captive lineages were used to create breeding populations.

Uncertainty about these populations, however, left skeptics wondering if some of these wolves descended from hybrids with domestic dogs. The evidence was anecdotal, Fitak said, but traits like floppy ears, which occasionally appeared, provided fodder to challenge the reintroduction program.

As part of his PhD work at the University of Arizona, Fitak and his team genotyped 87 Mexican wolves, mostly using blood and tissue samples from the Museum of Southwestern Biology in Albuquerque, New Mexico. The samples came from individuals from each of the captive linages and from cross-lineage wolves. Researchers examined more than 172,000 variances throughout the genome — far more than the few dozen markers that researchers previously were able to look at. They compared what they found in these wolves with genotypes from other studies of wolves in Alaska and Europe and with domestic dogs.

They found Mexican wolves shared an average of 0.06 percent ancestry with domestic dogs. What little shared genetics they found was most likely due to ancient ancestors shared by both Mexican wolves and domestic dogs, not hybridization.

“Overall,” they concluded, “our results suggested that Mexican wolves lack biologically significant ancestry with dogs.”

Some hybridization has occurred with domestic dogs since the reintroduction program began, Fitak said, but managers have worked to remove those from the breeding population.

“We don’t want to say there aren’t concerns and issues — and there should be more communication and networking between ranchers and managers — but this should hopefully provide a lot of support that hybridization with dogs is not one of them,” Fitak said.

Header Image: Reintroduced Mexican wolves are descended from three captive populations, prompting skeptics to question if these wolves were hybrids with domestic dogs. ©USFWS