Western Gray Wolf 25 Years

This Jan. 24, 2018 National Park Service photo shows a wolf from the Wapiti Lake pack in Yellowstone National Park, Wyo.

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A recent study indicates the genetic diversity of wolves in Yellowstone National Park impacts the severity of symptoms they experience from mange. The finding could also further research on conservation biology and scabies in humans.

Sarcoptic mange is a microscopic mite that burrows into the skin of animals and lays eggs. In wolves, it causes inflammation and infection, which often triggers relentless itching, scratching and hair loss. In humans, the mite causes scabies — a parasitic infestation that impacts an estimated 200 million people worldwide, according to the World Health Organization.

In September, a group of researchers led by Alexandra L. DeCandia, a former graduate student with Princeton University, published a paper in Evolutionary Applications that showed Yellowstone wolves with more diverse genes tended to experience milder mange symptoms.

Their paper — “Sarcoptic mange severity is associated with reduced genomic variation and evidence of selection in Yellowstone National Park wolves (Canis lupus)” — incorporated 25 years of observational data and hundreds of genetic samples from Yellowstone’s wolves.

“Genetics provide us with a really powerful tool for understanding wildlife health and conserving at-risk species,” DeCandia said, according to a news release. “We can learn more about the causes of disease, the short- and long-term effects on individual animals and populations, and how best to respond as wildlife biologists and managers.”

DeCandia has since completed her Ph.D. and is now a postdoctoral researcher at the Smithsonian Conservation Biology Institute, according to Princeton University.

Dan Stahler, a wildlife biologist for the park and a contributing author on the study, said biologists have been building population pedigrees based on genetic samples taken from wolves over the past 25 years.

Wolves from two different areas in Canada were reintroduced into Yellowstone in the mid-1990s. They were vaccinated for diseases, but scientists weren’t sure what the wolves’ disease ecology would look like in the long term, Stahler said.

DNA was collected from wolves in the park when they were captured or found dead. The long-term monitoring helped scientists track how wolves in the park were related to one another and how their genes varied.

For the recent study, biologists scored individual wolves on their genetic diversity based on the data. The study found that individual wolves with higher genetic diversity scores experienced less severe mange than wolves with lower genetic diversity scores.

“We leveraged the power of our population pedigrees and our DNA samples with the behavior, survival and pack structure,” Stahler said. “Then ultimately, we were able to show that mange severity varied across our population, depending on individuals’ genetic makeup.”

Sarcoptic mange made its way into Yellowstone’s wolf population in 2007, though records indicate the mite was intentionally introduced into coyote populations in the early 1900s, Stahler said.

“It was sort of like biological warfare,” he said.

Wyoming’s wolves began contracting mange in 2000, but it didn’t show up in the park until 2007. That year, the mite took off in Yellowstone. It was particularly prevalent in the northern part of the park where wolf densities were higher.

After sarcoptic mange reached Yellowstone’s wolves, biologists noticed that the severity of symptoms ranged significantly. Some infections were mild, while others were severe. Wolves with severe symptoms lost their fur and often wouldn’t survive the winter.

Biologists wondered what was causing the variation in symptoms, so they used the long-term ecological data to study the disease’s impacts. Since the disease is very visible, it was relatively easy for scientists to take detailed observational data, according to Stahler.

Researchers found that wolves with greater genetic diversity had greater resiliency to sarcoptic mange and appeared to recover at higher rates. The data and findings could be applied to mage in other species and scabies in humans, according to Stahler.

“If you can identify the genetics underlying disease severity in any living being, that is very promising and a powerful tool to target that for future treatment therapies down the road that can apply genetics,” he said.

The data taken on wolves could also help inform conservation efforts for other species, according to Stahler.

It shows that to maintain genetic diversity in any species, it’s important for the species to have large populations that can move across the landscape and exchange genes, he said.

“The future of species like wolves will really rely on having long term genetic diversity and connective populations,” he said.

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Helena Dore can be reached at hdore@dailychronicle.com or at 582-2628.

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