Wolves are thought of as red-meat eaters, but a team of biologists in northern Minnesota, near Voyageurs National Park, has documented a pack that often enjoys a meal of fish.

It is a rare glimpse of wolves catching and eating freshwater fish, although they have been observed eating spawning salmon along the coast of British Columbia and Alaska. The discovery was just published in the journal Mammalian Biology.

Wolves in Yellowstone have been known to chow down on trout, but it’s unclear whether they actually caught the fish or if the catch was already dead. “It is exceedingly rare, but they do it,” said Douglas Smith, the park’s wolf biologist.

Wolves were collared by the Voyageurs Wolf Project for research into pack territory and prey, primarily beaver but also deer fawns and moose calves. If wolves spent more than 20 minutes without moving, researchers went to the site to see if they were eating and if so, what it was.