Voyageurs National Park wolves eating beaver and blueberries, but not moose
When they aren't identifying record large trees in the forest, Thomas Gable and Austin Homkes' day job is wolf research, trying to untangle the complex, mostly unknown relationship between wolves and beaver in Voyageurs National Park.
They live-trap wolves and place GPS collars on them in the early spring and then follow the packs around from April to October, checking out exactly what wolves eat.
Researchers have known for decades that wolves eat beaver, but not how much. What Gable and Homkes found is that some wolves are getting nearly half their summer meals from beaver.
"We've seen some packs at 8-to-10 percent beaver in their summer diet to as much as 42 percent for one pack," Gable said.
At any one time there are six to eight wolf packs using at least part of Voyageurs National Park in their home range. Those packs average about five wolves per pack. Researchers had collars on 18 different wolves this past summer out of a total of 30 to 40 animals.
The abundance of beaver in the area may be taking some of the predator pressure off of the park's moose herd. While not a large population — there are about 40-50 moose in the park at any one time — the park's moose numbers have remained stable while their numbers have crashed across nearly all of Minnesota's moose range.
"We've found that the wolves here are not targeting moose. Over four years, going into more than 400 kill sites, we've only seen one adult moose taken by wolves," Gable said. "It's possible their focus on beaver might be helping the moose, at least when beaver are available in the summer. That's what we're trying to tease out here."
But it's already clear, the researchers say, that many wolves in the park choose to hunt and eat beaver in the summer instead of moose and deer.
The effort, overseen by the National Park Service, is funded through a state conservation grant from the Legislative and Citizens Commission on Minnesota Resources.
"What we are finding is both surprising and fascinating, but mostly because either no one looked closely enough at the wolf-beaver relationship before and/or the technology needed to really study the behaviors was only recently developed,'' said Steve Windels, National Park Service biologist at Voyageurs.
The research, which offers a new GPS-pinpoint location of each collared wolf 72 times a day, has found other surprising news. The park's wolves eat blueberries. Lots of them. Most of the wolf packs have been found to spend extended periods of time in July and August, during peak blueberry season, foraging in blueberry patches.
"There's been anecdotal stories and some research before that noted wolves will eat blueberries. But we were really surprised to see how much time they are spending on blueberry hillsides in July, early August. They are clearly targeting it as a food source,'' Gable said. "We don't know why. Maybe it's because it's at a time of year when it takes too much energy to (kill a deer or beaver) or what. But they are keying-in on blueberries."
Windels said North American wolves have always been thought of as carnivores but that they may have more omnivorous diets than previously believed. Wolves eating a lot of blueberries "still blows me away,'' he said.
The Voyageurs research, which covers multiple wolf packs in a relatively small geographic area, also has revealed some interesting insights into wolf pack behavior. Mapping the routes of GPS-collared wolves in multiple packs reveals the kind of interaction wolf packs have. Namely, none.
It's been well known for years that wolf packs often battle viciously to protect hunting grounds but with the GPS mapping "it's pretty amazing to visualize how much they avoid each other,'' Gable noted.
The color-coded pack activity map was posted last week and already has had more than 100,000 pageviews on Facebook.
"The boundaries between these packs are mostly invisible to people. But to the wolves, it's very, very obvious, and they respect it almost always, except for the occasional lone wolf passing through," Homkes said. "Sometimes it might be a river or a lake but, usually, it's just scent. Nothing we'd notice" in the forest.
To see more about the wolf research in Voyageurs National Park go to facebook.com/VoyageursWolfProject.