INTERNATIONAL FALLS, Minn. -- Anyone who has spent much time in the north woods knows how much beavers can impact a landscape, cutting trees, building dams, flooding low areas and slowing streams.
But what happens when a wolf takes out the dam builder?
It turns out the impact is just as profound, with dams quickly deteriorating and water draining from the ponds, meaning wolves — the apex predator in the state's north woods — are helping shape the very landscape they live in.
That was the finding of a new study by researchers in the Voyageurs Wolf Project who have been following wolves and their prey in and around Voyageurs National Park since 2015.
The results were published Nov. 13 in the journal Science Advances.
“It was sort of a simple premise. That a dead beaver can’t build a dam … But we wanted to look beyond that and see what the long-term implications are,’’ said Tom Gable, the lead researcher on the project for the University of Minnesota’s Department of Fisheries, Wildlife and Conservation Biology.
The four-year research effort found that, in an average year, wolves prevent about 88 ponds (filled with more than 50 million gallons of water combined) from being created in Voyageurs. That’s not a lot across the 772 square-mile study area in and around the national park. But over time, that’s hundreds of ponds that aren’t built, or that dry up, and that impacts not just wetlands, but also the forest and other wildlife around them.
“It’s a very profound impact on that specific area of the forest that doesn’t get turned into a wetland,’’ Gable said. “But it’s also impactful, over years, over the larger landscape.”
It’s the latest in a long line of stunning discoveries about the state's northern wolves made by the Voyageur’s Wolf Project, including first findings of summer wolf behavior that had been largely unknown before because most wolf research has been conducted in winter. The project documented how wolves will sit and wait to ambush prey and not just follow and chase prey as had been previously believed. 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.
Back in 2015, Gable and field researcher Austin Homkes found where a wolf had killed a young beaver that had just been kicked out of his mother’s home pond to make a new pond for himself.
“Within days of the wolf killing the beaver, the dam failed because there was no beaver left to maintain it,’’ Homkes said. That prevented more trees from flooding or being cut by the beaver. And that beaver pond from 2015 still has not been colonized by another beaver, said Gable, who visited the site in mid-September this year.
The wolf project has been among the first to document just how many beavers wolves kill to eat. It turns out that it’s far fewer than expected. Voyageurs has a “dense’’ beaver population “they are everywhere here,” Gable notes. But only 25%-35% of a Voyageurs wolf summer diet is beaver. (For some wolf packs that have learned to ambush beavers better, beavers are up to 42% of their summer food.)
“I think the old thinking was that wolves can grab a beaver whenever they want in the summer,’’ Gable said. “But it turns out that it’s far more difficult, and far less common, for a wolf to kill a beaver than most people think. Beaver up here can be 60 pounds, nearly the average weight of our wolves. And there’s no easy place for a wolf to grab a beaver. It’s like biting a 60-pound football.”
Beavers also know where they are safest and so don’t spend a lot of time on land. Once in deeper water, wolves can’t catch them. In the winter, beavers are safe from wolves in their fortress beaver houses.
“We tried to put up a trail camera to get beavers and we could go two weeks, even in a likely looking spot near a dam, without seeing one on land,’’ Gable said. “So imagine how hard it is for a wolf to pick the right spot to sit and wait for a beaver to come by.”
On average, there are about 73 wolves in the Voyageurs area but that can fluctuate annually between 63 and 82, spread between multiple wolf packs.
Despite the best effort by wolves, there’s no evidence that beavers are in short supply in the park which has among the highest beaver densities anywhere in the U.S., said Steve Windels, a co-author of the study and a National Park Service wildlife biologist.
"The fact that we have convincingly shown wolves can impact wetlands without necessarily changing the abundance or behavior of beavers is a really exciting finding," said co-author Sean Johnson-Bice, a University of Manitoba researcher who worked on the beaver study.
Federal wildlife officials announced last month that the gray wolf would be removed from U.S. Endangered Species Act protection, leaving management decisions to states and tribes and opening the door to hunting in some. But wolves in the park would remain off limits to any hunting and trapping, under federal law, and Minnesota Gov. Tim Walz has said he opposes recreational wolf hunting.
Even under their federal threatened status here, however, more than 200 wolves, including some just outside the park, are killed every year in Minnesota under a federal program to trap and euthanize wolves near where livestock have been killed.
Funding cut off
The Voyageurs Wolf Project has until now been funded by the Minnesota Environment & Natural Resource Trust Fund with money from the state’s lottery profits. But the 2020 Minnesota Legislature failed to pass a trust fund bill leaving dozens of conservation and research projects across the state without funding. The funding bill, while not controversial, was caught in the crossfire of the divided Republican-DFL Legislature.
That includes $575,00 that would have been earmarked for the Voyageurs Wolf Project to keep research going into 2023.
“We essentially run out of money in December,’’ Gable noted, saying he will stay on, unpaid if necessary, to keep the project going as long as possible. “I’m optimistic that the ENRTF money may still be approved at some point, or that some other funding sources might come through. But the future is pretty uncertain right now.”