In another stunning revelation of wolf behavior from Voyageurs National Park, researchers Thursday announced they have confirmed park wolves hunting for and eating fish out of streams as a regular part of their diet.
The researchers released the first-ever video of wolves eating freshwater fish, and said GPS data shows one pack spent about half their time during several weeks in April and May "hunting" in creeks for spawning suckers and northern pike.
The revelation comes just one week after the News Tribune first reported the same researchers confirming wolves spent weeks on end in blueberry patches, eating blueberries at peak summer ripeness. The same researchers also are the first to document wolves' consuming large numbers of beaver, when the animals are available in summer months, and that wolves will leave deer and moose alone if they can get beaver as meals.
There's some speculation that the wolves focus on beavers - and maybe now on fish - has helped keep the park's moose population stable at the same time moose numbers have crashed across most of their Minnesota range.
The Voyageurs Wolf Project, a collaboration between the University of Minnesota and Voyageurs National Park, has followed GPS-collared wolves from over seven different packs since 2015. The fish revelations were recently published in the journal Mammalian Biology.
Using GPS collars, the team collects location data from wolves every 20 minutes. That data reveals not just wolf behavior but also pack territory boundaries.
Researcher Tom Gable first noticed the wolf-fish interaction in April, 2017, when he hiked to a creek where GPS data showed one of the collared wolves was spending a lot of time. "As I approached the area, I briefly saw a wolf trying to catch a fish before it ran into the woods," Gable said. He then found fish remains and wolf tracks scattered along the creek.
In the following month the team found the two GPS-collared wolves in the Bowman Bay pack, south of Lake Kabetogama, spent 43-63 percent of their time hunting fish around this creek.
The same behavior was seen again in early spring 2018, and the team quickly deployed several trail cameras to gather more evidence. By the end of the season they recovered the footage of this rare behavior, including wolves fishing at night.
"The wolves are standing next to the creek in the dark, just listening or looking," Gable said, referring to the video. "You can see the wolves abruptly head to the water several times after hearing a splash. They learned what a fish splashing in the creek sounds like and they know that it means food. Incredible."
While fish were not the primary prey over the course of the summer, they appear to be an important food source at a key time of year, and the revelation shows just how adaptable wolves are.
Wolves are known to eat spawning salmon in coastal British Columbia and Alaska, but wolves hunting freshwater fish has not been described in detail before. But Joseph Bump, University of Minnesota professor overseeing the research, said wolves eating fish in Minnesota isn't surprising. Getting the evidence was the hard part.
"Since wolves are a difficult species to document, especially in the densely forested areas of northern Minnesota, you have to either be in the right spot at the right time or have access to GPS-collar data,'' Bump said.
Gable and fellow researcher Austin Homkes also have published color-coded maps on social media that show the GPS-followed wanderings of the park's multiple wolf packs. One of those images clearly shows how the packs avoid each other's territories. Again, while researchers have known for years that wolf packs avoid each other, it was the Voyageurs' research unique use of GPS telemetry that allow them to develop an image that clearly showed that behavior to the public. The image has nearly 50,000 views on Reddit. The researchers also confirmed that wolves will commonly swim long distances - nealy a mile across open water in the lake-studded park.
Voyageurs National Park is relatively small at 227,000 acres on the Minnesota-Ontario border, much of which is comprised of large lakes including Kabetogama, Namakan, Sand Point and Rainy. It's Minnesota's only national park, much of which is accessible only by water. Unlike the nearby Boundary Waters Canoe Area Wilderness, Voyageurs is open to motorized boat and snowmobile traffic in many areas.
The Minnesota Department of Natural Resources estimates about 2,800 wolves live in the state, mostly in the northern third of counties, by far the most of any state outside Alaska.
The park wolf research can be followed at facebook.com/VoyageursWolfProject.