Study: Wolf Population high enough to maintain Genetic Diversity

Some old research is providing new insight into the genetic diversity of wolves in the Northern Rockies.

Authored by well-known names in the world of wolf reintroduction, the newly published study concludes that as far back as six years ago, wolf numbers were high enough to avoid genetic stagnation in the region.

Mark Hebblewhite, a University of Montana ecologist and longtime wolf researcher, said the study is the most comprehensive paper ever completed on a wild population of carnivores.

Using a combination of genetic samples gathered from all 66 wolves reintroduced into Yellowstone National Park and central Idaho and extensive information by tracking radio-collared wolves, the study showed there was a substantial amount of genetic mixing between the three population segments in Montana, Idaho and Wyoming.

“It was a groundbreaking way to track gene flow between isolated populations,” Hebblewhite said. “Essentially, they made a huge family tree of the wolves they studied.”

Hebblewhite co-authored a perspective on the study for October’s edition of Molecular Ecology.

The study was authored by the same team that earlier reported wolves in Yellowstone National Park were genetically isolated. That information was used to argue against delisting the Northern Rockies population in 2008.

The newly published study – “using an impressive sampling design and novel analytic methods” – showed substantial levels of gene flow between the three identified subpopulations of wolves in the Northern Rockies in the years leading up to 2004, according to the Molecular Ecology article.

Both Hebblewhite and longtime wolf biologist Dave Mech said the findings that wolves were intermixing between Yellowstone, central Idaho and northwestern Montana was not surprising.

Both said they’ve seen wolves move great distances in a short period of time on many different occasions.

“Wolves are born to move,” Hebblewhite said. “I’ve seen a wolf move 50K in 24 hours. … It’s absolutely nothing for these things to move all over the place.”

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Mech was part of the original team that helped with the wolf reintroduction efforts. The University of Minnesota professor has studied wolves and their prey since 1958.

Wolf biologists have known for years that wolves were moving between the three populations, but never had the science to prove it, he said.

“This isn’t just an academic issue, it’s also a legal one,” Mech said in a telephone interview. “Lawsuits have maintained that wolf populations are not large enough to have genetic interactions. This study proves that they do.”

Mech said it was important to note the research paper was written by the same team that earlier maintained there wasn’t genetic interchange occurring inside Yellowstone National Park.

“They recognized the flaws of their first study,” Mech said. “Science is self correcting. … It’s far better to do that yourself than have someone else do it.”

The new study expanded the region around the national park to include the greater Yellowstone ecosystem where the wolf population was lower.

Hebblewhite said the initial study focused specifically on Yellowstone National Park, which was likely already at carrying capacity for wolves.

“At that point, it was probably difficult for a dispersing wolf to successfully migrate into there,” he said.

The research for the most current study ended in 2004. At that point, wolf numbers in the three states were less than half of what they are today.

The latest official count put wolf numbers in the three states at about 1,700. And that number doesn’t include this year’s offspring, Mech said. He estimates the numbers now are closer to 2,000.

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The new study’s findings don’t clear up a prevailing debate over just how many wolves are enough to create a sustainable population in the Northern Rocky Mountains.

The original population recovery goals set at 300 wolves distributed in at least 10 breeding pairs in Montana, Idaho and Wyoming were met years ago.

The conservation community has long said those numbers were too low.

Mike Leehy of Defenders of Wildlife said the new study suggests that genetic connectivity between different populations may not fare well if wolf numbers drop as low as those original recovery goals.

“This study is a step toward the science we would like to see to help determine how many wolves are needed for the long-term health of the wolf population in the region,” Leehy said.

That science has never been done before, he said.

Hebblewhite said this science could prove to be important in future judicial decisions on the wolf’s status as an endangered species.

“Judges tend to favor genetic evidence,” he said.

The study also proved beyond a doubt that wolves now living in the Northern Rockies did not somehow contaminate a remnant native wolf population.

“That whole notion is just nonsense,” Hebblewhite said. “The wolves from Canada were coming here by themselves. … They were already here. They walked.”

The study is titled “A novel assessment of population structure and gene flow in grey wolf populations of the Northern Rocky Mountains of the United States.” Its authors are:

Bridgett vonHoldt, Daniel Stahler, Edward Bangs, Douglas Smith, Mike Jimenez, Curt Mack, Carter Niewmeyer, John Pollinger and Robert Wayne.