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Study says wolves in Midwest help reduce deer-car collisions



A wolf in Yellowstone. A new study says its cousins in the Upper Midwest are affecting the behavior of white-tailed deer and it’s yielding fewer car wrecks. PHOTO COURTESY OF JIM PEACO/NPS

By Todd Wilkinson EBS Environmental Columnist

Landscapes where gray wolves roam have fewer deer-human vehicle collisions on local highways. 

That’s the provocative finding of a new scientific analysis focusing on counties in northern Wisconsin, but it could hold implications for other wolf-inhabited parts of the Lower 48, one of the study’s three authors said. 

In fact, this revelation is among several insights featured in the peer-reviewed scientific paper published May 24 titled “Wolves make roadways safer, generating large economics returns to predator conservation.”

The findings are timely, for they challenge many conventional negative portrayals of wolves used by states in 2021 to sanction a new era of mass wolf killings, often based upon claims that lobos represent only economic liabilities imposed on ranchers, farmers and hunters. 

After crunching numbers available in different data sets, researchers say higher wolf presence translates, on average, into a 24-percent reduction in deer-vehicle collisions in Wisconsin counties. Even more poignant: the economic savings realized in deer-vehicle accident reduction is 63 times greater than the costs of verified wolf predation on livestock.

In blunt terms, the economic value of wolf existence vastly outweighs the economic costs to farmers when wolves kill cattle, sheep or other domestic animals.

Moreover, in the same North Woods of the Upper Midwest where white-tailed deer numbers have exploded in recent years and caused crop damage in farmer’s fields, wolves help regulate deer overpopulation. In so doing, they may aid in controlling high deer numbers linked to spread of tick-spreading Lyme disease and other epizootic maladies. 

The paper contains a lot to unpack, beginning with the correlation between wolves and collisions involving deer and vehicles. “Most of the reduction [in deer-vehicle collisions] is due to a behavior response of deer to wolves rather than through a deer population decline from wolf predation,” write the paper’s three authors, Jennifer L. Raynor and contributors Corbett A. Grainer and Dominic Parker. 

“Our study suggests that systematic elimination of wolves from North America has also caused unintended damages,” the paper states. In Wisconsin, wolf presence reduced deer-vehicle losses by an average of $375,000 per county, per year and by $10.9 million annually in aggregate across the 29 wolf counties.  

“As a point of comparison, the state paid $3.1 million in compensation to individuals for verified deaths or injuries caused by wolves of livestock, hunting dogs, and pets between 1985 and 2019 or an average of $174,000 per year over the last five years” the paper continues. “The economic benefit of reduced deer-vehicle collisions exceeds the economic costs of verified wolf predation by a ratio of 63:1. This ratio is relevant because economics matters for listing, delisting, and management decisions for endangered species, is only as implicit considerations.” 

Of note is that the reduction in collisions happens primarily in rural areas where livestock predation occurs. “This finding may help dampen political polarization around wolf reintroduction that generally pits rural and urban voters against one another, as was the case with the November 2020 vote on wolf reintroduction in Colorado.” Coloradans narrowly passed the referendum calling upon state wildlife officials to bring wolves back to the Centennial State.  

The authors also reference the widespread challenge of deer-vehicle collisions that occurs because of where highways pass through habitat and that it’s not an easy or inexpensive problem to fix. Having wolves could be a cheaper way to mitigate rather than having to employ costly engineering solutions. 

Of interest to those familiar with wolf issues in the West, they allude to some pioneering findings in Yellowstone National Park showing that wolf presence creates a “landscape of fear” for ungulates like elk, keeping those prey species constantly on the move, reducing foraging pressure on aspen trees and yielding positive ecological ripple effects. 

The authors also note that the beneficial effect of wolves in Wisconsin causing deer to avoid roadways where they’re more vulnerable to wolf predation could not be achieved by hunters. 

“[Our] finding supports ecological research emphasizing the role of predators in creating a ‘landscape of fear,’” they note. “It suggests wolves control economic damages from overabundant deer in ways that human deer hunters cannot.”

According to Parker, one of the authors, not only are hunter numbers falling but hunts occur only seasonally while wolves are active all year long. The same argument applies to the beneficial role wolves can play in slowing the spread of Chronic Wasting Disease in the West. While states employ hunter culling of ungulates in areas where CWD prevalence of deer family members is high, wolves actually have an ability to target animals that are sick and remove them, potentially helping to eliminate disease spreaders. 

Regarding wolves as allies to farmers, when lobos reduce the size of deer populations it lessens their impact on crops. In Wisconsin, deer cause 90 percent of all wildlife-related damage to agriculture. 

“The finding that wolves reduce deer-vehicle collisions primarily by changing deer behavior rather than by reducing deer abundance is likely good news for policymakers,” the authors note. “It implies they do not need to choose between a $20.6 billion nationwide recreational deer hunting industry and deer-vehicle benefits from wolves. At least in Wisconsin, it seems that wolves and deer hunters can coexist with safer roadways.”

The paper’s findings are especially timely given recent events in the Northern Rockies. This winter and spring, lawmakers in both Montana and Idaho passed legislation, signed into law by governors, that essentially greenlights action to re-eradicate recovered wolf populations.

Todd Wilkinson is the founder of Bozeman-based Mountain Journal and is a correspondent for National Geographic. He also authored of the book “Grizzlies of Pilgrim Creek,” featuring photography by Thomas D. Mangelsen, about famous Jackson Hole grizzly bear 399.

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