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The number of grey wolves in and around Voyageurs National Park in far northern Minnesota dropped by 19 percent compared to last year—and by about 31 percent over the past two years— according to a new report from researchers who have intensively studied wolves in the region for over a decade.
Researchers with the Voyageurs Wolf Project counted 99 wolves, including 22 lone wolves, in the area spanning the national park near International Falls and a large chunk of land south of the park. That’s the lowest number of wolves in the area in the past eleven years—nearly equal to another low point in 2020.
But the drop wasn’t that surprising to Tom Gable, who leads the project. That’s because the number of deer in the area dropped by more than 50 percent over the past three to four years, following back-to-back harsh winters in 2021-22, and 2022-23.
“And so we were anticipating that the wolf population was very likely going to follow suit, as their main food source had declined. And that's exactly what we ended up seeing,” explained Gable.
As the deer population dropped, the wolf population responded in two significant ways, Gable said. First, fewer wolf pups survived. The average pack in their study area only reared one pup to adulthood. That’s a survival rate of about 20 percent, compared to a typical survival rate of around 30 or 35 percent, as packs struggled to find food to feed their young ones.
Secondly, wolf pack territories expanded by more than 50 percent compared to just two years ago, to nearly 150 square kilometers on average this past year.
That’s a strong indication that deer density was low.
“Wolves have to increase their search effort, have to expand the area that they're looking for prey, because their former territories a couple years ago simply were not large enough to have enough prey that could sustain the wolf population, or at least that pack,” Gable said.
That increased territory size resulted in fewer packs in the region. Researchers counted 19 packs this past year, compared to 22 the year prior, meaning that three packs disappeared and their territories were absorbed by neighboring packs.
Gable said it’s difficult to know whether their report reflects statewide wolf population patterns. The latest study from the Minnesota Department of Natural Resources in 2023 estimated about 2,900 wolves in the state. The population has hovered between roughly 2,500 and 3,000 wolves for the past few decades, as Minnesota has the largest number of wolves in the lower 48 states.
Researchers with the Voyageurs Wolf Project deployed 378 trail cameras throughout their study area, about 15 to 20 per pack. That allows them to get repeated observations of wolves throughout the winter.
They also place GPS collars on wolves that report locations every 20 minutes, which allow researchers to see the specific locations of wolf pack territory boundaries.
Researchers stress that the area “still supports a stable moderate-to-high density wolf population,” despite the drop in numbers. They say it’s simply part of the natural ebb and flow of wolf numbers as they respond to deer populations and winter trends.
Long winters where snow lingers into early May are especially challenging for deer, because trudging through deep snow zaps their energy and makes it more difficult to find food and evade predators.
Wolves come out of those harsh winters in good shape, healthy from a steady diet of vulnerable deer. As deer numbers drop, they can sustain themselves for a time on other food sources and their fat reserves. But eventually, those low deer numbers catch up to wolves, Gable said.
“And that's basically what we’ve seen in the past two years. It took the population a little bit to kind of respond to that reduction in deer density.”
But the population seesaw between wolves and deer could soon teeter the other way. Two consecutive mild winters have allowed deer populations to recover a bit, and if that pattern continues, wolf populations will likely follow suit, researchers say.
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