Wolves are key for having healthier moose, study finds

New research suggests wolves are more effective than humans at culling moose in a way that improves the overall health of their population — an argument that could bolster calls to keep the predators in the wild.

While human hunters may eye healthier prey, researchers at Michigan Technical University found wolves seem to selectively target animals suffering from genetic diseases like osteoarthritis — helping reduce the prevalence of those diseases in the animal population.

“Wolves might be an effective, natural, and more ethical way of regulating the health of deer and moose populations – as opposed to using culls or recreational hunting to reduce the incidence of diseases or parasites of concern,” Sarah Hoy, one of the lead Michigan Tech researchers involved in the study, said in a statement.

The study builds on research that suggests wolf packs have broad positive effects on the ecosystems to which they’ve been introduced, rolling back the ecological damage from overpopulation by hoofed mammals like moose, elk and deer.

But it also comes against a backdrop of controversy, with recent state and federal numbers showing wolf killings up in Oregon, Colorado, New Mexico and the Yellowstone Valley.

The study team surveyed data spanning nearly five decades, focusing on animals killed by wolves on Michigan’s Isle Royale, home to a moose population and a wolf colony that arrived in 1948. 

They found that wolves tended to disproportionately kill older moose as well as younger ones suffering from osteoarthritis — a progressive, genetically-linked bone disease marked by the breakdown of cartilage around joints.

That behavior makes sense, Hoy said, because “adult moose weigh between 800 and 900 pounds, which is between eight and 10 times as heavy as a wolf.” In other words, wolves are going after older and perhaps more vulnerable moose to better the odds.

What was more surprising was the possible impact on the moose gene pool. The more of the large herbivores killed by wolves in a given year, the lower the rate of osteoarthritis in the surviving population.

Past research has pointed to the effects of wolves being being introduced in certain ecosystems.

In Yellowstone National Park, for example — where wolves were reintroduced in 1995 after their eradication in 1926 — the presence of wolves led to a ripple-effect “across the entire structure of the food web that defines biodiversity in the Northern Rockies ecosystem,” according to a 2014 study in PLOS One.

But a record number of Yellowstone wolves — 25, about 20 percent of the national park’s population — were shot by hunters this winter after neighboring Montana, Idaho and Wyoming changed state laws to allow hunts of wolves who strayed from the park, The Associated Press reported.

While these hunts were legal — though controversial — some other killings of wolves this winter were not. 

Twenty-one wolves were killed by humans in Oregon in 2021, including eight killed illegally by poison, according to a report by the state’s Fish and Wildlife Department.

And 119 Mexican gray wolves were illegally killed by humans between 1998 and 2020, according to a federal Fish and Wildlife conservation plan released this month.

In February, a federal judge restored the protections that then-President Trump had stripped from gray wolves in 2020. That relaxation of the law had allowed a 2021 Wisconsin trophy hunt that killed 200 of the animals.

Environmental groups touted the latest research to emphasize the importance of maintaining wolf populations.

“This study highlights the ecological importance of wolves, which improve the health of moose by targeting the old and diseased,” said Collette Adkins, carnivore conservation director at the Center for Biological Diversity. 

“Because wolves are so valuable to the health of our wild places, it is tremendously wasteful to allow them to be gunned down by trophy hunters.”