By Karen Hopper Usher
EAST LANSING — A rivalry between predators is playing out in the forests of Wisconsin and Michigan’s Upper Peninsula.
It’s wolves vs coyotes vs foxes, and the effects of this competition are felt on down the food chain to deer mice, according to a recent study published in the Journal of Mammology.
Coyotes are like jerk roommates that steal your food, said David Flagel, the study’s lead author. That’s why wolves hate the fellow canid.
The story of the rivalry plays out on remote property owned by the University of Notre Dame that is home to a naturally rebounding wolf population, said David Flagel, the study’s lead author. Wolves have come back because of protections placed on the animals by the Endangered Species Act.
Their resurgence at the property in northern Wisconsin and Michigan’s Upper Peninsula provides a good opportunity to study an ecological concept called “trophic cascades.”
Flagel translates that phrase as “the enemy of my enemy is my friend.” A classic example of a trophic cascade is when a large predator helps vegetation by eating the animal that would have eaten the plants. Related story.
But the evidence of trophic cascades applying to predator relationships was a bit thinner. Flagel, now the assistant director for the University of Notre Dame Environmental Research Center – West (in Montana), investigated that relationship with the help of the Michigan Department of Natural Resources and Ohio State University.
Just as wolves and coyotes don’t much like each other, the same is true of foxes and coyotes. Competition for food causes the strife.
Wolves like to take down something big, like a full-grown deer, gorge themselves, then pass out. While they sleep, the coyote steals the leftovers.
While awake, wolves and coyotes compete for fawn. So the wolves chase, harass and sometimes kill coyotes.
It’s much the same between coyotes and foxes. Coyotes see foxes as competition for hares, and so they chase and kill foxes.
Wolves and foxes, though, have less in common, food-wise. What they do have in common is a dislike of the coyotes that try to rob them of their respective lunches.
Flagel’s team wanted to study whether the rebounding wolf population would affect coyotes and foxes.
Counting the canid population on the property meant counting piles of scat. Researchers did this monthly from May to October during 2008-2014. They looked for the scat on the 8,000 acre property’s gravel roads.
Humans aren’t the only mammals that use roads. Dog species like wolves, coyote and fox tend to use roads strategically to mark their territory because the open space helps wind move their scent around, Flagel said.
What they found was that areas with high wolf-use had fewer coyotes and more foxes. The coyotes were using the wolf areas 51 percent less than the wolf-free areas. But foxes used the wolf area almost exclusively (a 10-to-1 ratio). And the effect was observed on down to snowshoe hares and deer mice. Coyotes eat snowshoe hares, and evidence of snowshoe hares was three times as common in high wolf-use, low coyote-use areas.
It’s not easy to take an animal census.
Researchers used damage to tree saplings, or “hare browse” to estimate the hare population because hares leave a distinctive mark when they eat.
That method isn’t as good as physically counting hares, said Brian Klatt, director of the Michigan Natural Features Inventory.
“But I also know how hard it is to monitor this many species,” Klatt said. Overall, the study was solid.
“It certainly makes sense,” he said.
Hare browse tripled in the wolf-and-fox zone. Flagel said. Deer mice, which foxes eat, were generally less common in the wolf zone in some years.
To understand the implications of the cascading effects from wolves, you need to understand the history of wolves and coyote.
We’ve gotten used to the presence of coyotes, but it wasn’t always that way, Flagel said. Up until the 1950s, there was a bounty on large predators like wolves, and as a result they were nearly wiped out from the eastern United States. At the same time humans were killing wolves, they were cutting down trees–making the landscape more friendly to coyotes, which prefer open areas. Coyotes expanded their range, and rabbit, hare and fox populations fell.
It’s what scientists call a “mesopredator release,” Flagel said. The mesopredator (medium-sized predator) is released from the conditions that keep it in check, and the effects are felt on down the food chain.
But now the wolves are coming back and there’s evidence of cascading effects caused by their return.
It shows the reversal of the effects of coyote taking over the eastern United States, Flagel said.
“What we’re seeing here is gray wolf recovery can benefit small carnivores and rabbits and hares by changing or redistributing coyotes, and also deer mice decrease in some years,” Flagel said.
This isn’t the first study that has looked at the impacts of wolves on our ecosystems, said David MacFarland, large carnivore specialist with the Wisconsin Department of Natural Resources. “But anything that adds to enhanced understanding is beneficial as we’re making management decisions.”
And it’s not just wolves that are coming back in the upper Midwest, MacFarland said. Bears are also more common than they were.
“Large carnivore communities are doing better than they have in the past hundred years,” he said. Meanwhile, large carnivores in other parts of the world are in “significant peril.”
Scientific reaction to the study has so far been positive, Flagel said. He’s been presenting his findings at wildlife conferences.
Flagel’s team was the first do a study like this at such a fine scale, Flagel said, and that’s important because that’s where the wolf, fox and coyote interactions are happening.
“You can actually see foxes avoiding coyotes, coyotes avoiding wolves,” Flagel said. Studies like these are an important first step in learning more about these systems with these species because it gives scientists information about what might happen next as large predator populations rebound.
If wolf populations continue to spread, Flagel thinks wolves will come to northern lower Michigan next and then possibly the Adirondack mountains.