New Study Reveals How Wolves Affect the Ecosystem of Isle Royale National Park by Hunting Beavers
About 15 miles from the Canadian province, there is a treasured copper mine, sitting in the middle of Lake Superior’s crystal clear waters. Screening within these groves is a drama played out by the most famous predator-prey pair residing in the park: the timber wolf and the beaver. While these wolves also prey upon animals like moose and snowshoe hares, beavers are relatively easy to catch and easier to kill, which is why they make up their top meal preference.
While beavers emerge from the water to cut wood stands and trees to hoard up for themselves and their kits, wolves spying from behind the bushes charge and pounce upon them, satisfying their bellies. Today, however, the scene has dramatically altered. According to a study published in Nature Scientific Reports, wolves in Isle Royale are exhibiting a sudden change in their lodging behavior, most likely driven by the changing habitats of resident beavers.
Researchers found that the gray wolves on Isle Royale are quietly aligning their habitat preferences with those of the beavers, triggering a ripple effect throughout the entire ecosystem. According to NPS, these wolves, also called “Canis lupus,” first arrived in this region by crossing an ice bridge that formed between the island and the Canadian mainland during the winter of 1948. Ever since, they have remained the dominant predator of the park, mostly patrolling its lakeshores, hiking trails, and open land.
To begin this study, researchers hypothesized that wolves' selection of beaver lodges depends on seasonal changes, such as the intensification of ice cover when beavers become vulnerable. At this time, beavers tend to spend more time away from their home lodges. Beavers, the architects of the ecosystem, ultimately determine the pattern of where and how the wolves will gravitate in the coming seasons.
“Beavers are ecosystem engineers by building dams that create impoundments. Large ponds that used to be moving water are now standing water, so that can actually affect the entire ecosystem that is now flooded,” Adia Sovie, study’s lead author and a Michigan State University researcher, said in a university press release.
To conduct the research, Sovie and her team utilized four years of GPS data of wolf habitat selection in relation to active American beaver lodge locations. They monitored 834 unique active beaver lodges in total, with 395 in 2018, 386 in 2020, 344 in 2021, and 168 in 2022. About 18,932 wolf GPS locations from 23 wolves were studied, including 10 females and 13 males. This data enabled the team to look into the details of the wolves’ locations relative to the location of the known active beaver lodges.
Sovie revealed that they found that wolves are really “dynamic in how they look for prey and select prey.” In about March through November, she said, wolves tend to hunt moose and their calves, and then during other times of the year, they are usually looking for beavers. “They’re looking for beavers, and we think that relates to the difficulty of hunting moose later in the summer,” Sovie said
Isle Royale has been home to beavers for decades. However, over the years, a degrading ecosystem has prompted a massive decline in the population of aspens, many of which have been cut down. And as the trees are chopped down, beavers find their main food source shrinking in supply. And as the buffet turns scanty, beavers gravitate elsewhere, which influences the trail wolves will take to procure their food, Rolf Peterson, a professor at Michigan Tech University and an expert in predator-prey interactions who was not involved in the study, shared.
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