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Waiting, sometimes for hours, wolves play the wind to ambush beaver

Voyageurs Wolf Project continues to break new ground on how wolves live, thrive, eat and die.

Voyageurs Wolf Project researchers Austin Homkes, left, and Thomas Gable inspect a site where a wolf had ambushed and ate a beaver in August 2019. The researchers this week published the first-ever peer-reviwed scientific paper on wolf ambushing behavior and success. (Steve Kuchera / File / News Tribune)

Back in August 2019, a reporter and photographer followed Thomas Gable and Austin Homkes as the two wildlife researchers crawled on hands and knees, on an island in Voyageurs National Park, inspecting a site where a wolf had killed a beaver.

It was one of hundreds of such sites the Voyageurs Wolf Project inspected, precise locations of wolf kills revealed by GPS satellite technology, that the researchers painstakingly studied to determine what had happened.

What they found at site after site, over five summers of that research, was nothing short of groundbreaking in wildlife science — that wolves don’t just chase and catch their prey to eat, they also lie in wait, ambushing prey such as beaver in places where they expect a beaver to pass by.

The results of that research was officially published this week in the journal Behavioral Ecology, one of several scientific, peer-reviewed papers the Voyageurs Wolf Project has published since the project started in 2015.


A pack of wolves in an image taken from a trail camera placed as part of the Voyageurs Wolf Project. (Photo courtesy of Voyageurs Wolf Project)

It is the first systematic analysis of wolf ambushing behavior and shows how highly flexible wolves are in deciding how to get a meal.

In winter, as is well-documented, wolves often hunt large prey like deer and moose in packs of several wolves by running the bigger animal down. But in summer, the Voyageurs Wolf Project documented, wolves often hunt alone. And ambushing is a good tactic if you are alone.

PREVIOUSLY: The secret summer lives of Voyageurs Park wolves Once a mystery, wolves' summer prey and habits are unfolding in ongoing study.
Specifically, the latest paper shows how wolf ambushing strategies are well suited to capture beavers, and that wolves appear to know beavers can't see very well and thus pick spots to capitalize on that weakness, like tall grass on a trail that the beaver uses to haul tree cuttings back to the beaver house or beaver dam. (The scientists even did a side experiment on just how bad beaver eyesight is, using cardboard cutouts with a photographic image of a wolf. Beavers seemed oblivious to the wolf decoy, paying it no attention at all, as shown in a downright funny trail camera video the project produced.)

But beaver’s sense of smell is very good, and wolves seem to know that, too, so wolves set up mostly downwind of where they expect the beaver to show up. Some 90% of the ambush sites were downwind of the beaver trail, exposing the remarkable ability of wolves to adjust their hunt based on wind direction.

In the water, where beaver spend most of their time, wolves can’t catch fast-swimming beaver. But on land, the beaver is vulnerable. Still, how does a wolf catch a semi-aquatic prey that spends little time on land and never ventures far from the safety of its pond?

"Turns out with patience and a lot of waiting," Gable noted. Wolves sometimes waited up to 12 hours for a beaver to show up, the study found.


“One wolf even waited in ambush for 30 hours,” Homkes said.

But it doesn’t always work. In fact, among the documented ambush sites, wolves killed a beaver less than 25% of the time.

A new study published this week documents for the first time how wolves will wait, sometimes for hours, downwind of where they expect a beaver to pass by, taking advantage of the beaver's poor eyesight. (Photo courtesy of Voyageurs Wolf Project)

“Over a five-year period, we estimate that our field research team collectively put in over 15,000 person-hours to search nearly 12,000 locations where wolves had spent time. Through this effort, we ended up documenting 748 locations where wolves waited to ambush beavers but were unsuccessful, and 214 instances where wolves killed beavers,” said Sean Johnson-Bice, a co-author of the study.

The researchers found that ambushing behavior wasn't unique to a few wolves. Instead, wolves from multiple packs across several years used the same tactics, indicating that this behavior is widespread throughout the greater Voyageurs ecosystem and likely other ecosystems where wolves hunt beavers.

New findings keep coming

The Voyageurs Wolf Project made headlines in December with a viral Facebook video that showed an entire year of trail camera photos in one place on one beaver dam, with dozens of different birds and animals showing up in photos.

PREVIOUSLY: A year on a beaver dam: Video captures remarkable diversity of wildlife in one spot Voyageurs Wolf Project distilled a year's worth of video and sound, taken in one location, into six minutes.
In November, the same scientists published a study of how wolf predation on beavers impacts the entire ecosystem by keeping many beaver dams dry rather than flooding nearby forest. It was the latest in a long line of stunning discoveries about Northland wolves made by the researchers, including first findings of summer wolf behavior that had been largely unknown before because most wolf research has been conducted in winter.


The project also documented wolves catching and eating fish out of a stream and spending weeks in blueberry patches to feed almost entirely on berries when they are ripe, both firsts for wolf research in Minnesota.

On average, there are about 73 wolves in the Voyageurs area, but that can fluctuate annually between 63 and 82, spread among multiple wolf packs. The Voyageurs Wolf Project is a joint effort of the National Park Service, overseen by Voyageurs Park wildlife scientist Steve Windels, and the University of Minnesota, where professor Joseph Bump is the project head. The project has used social media to better explain what they find to the public, and now has more than 61,000 followers on Facebook.

Voyageurs Wolf Project researchers Austin Homkes, left, and Tom Gable watch a video of a wolf that triggered the trail camera in the background. (Steve Kuchera / 2019 file / News Tribune)

The wolf project had been funded by the Minnesota Environment and Natural Resources Trust Fund that's stocked by the state's lottery profits. But that funding ran out this year when the Minnesota Legislature failed to pass a trust fund bill, leaving dozens of projects across the state without funding.

Gable said the project has cobbled together enough grants to fund partial field work in 2021, with reduced staffing, but that without the state funding, it's likely 2021 will be the last year for the project that had hoped to go on permanently, such as the Isle Royale wolf-moose study.

Voyageurs National Park is relatively small at 227,000 acres on the Minnesota-Ontario border, much of which comprises large lakes, including Kabetogama, Namakan, Sand Point and Rainy. It's Minnesota's only national park, and much of it is accessible only by water. Unlike the nearby Boundary Waters Canoe Area Wilderness, Voyageurs is open to motorized boat and snowmobile traffic in many areas.

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at jmyers@duluthnews.com.
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