The Wolves and Moose of Isle Royale Walked There Across a Bridge of Ice

Out in the cold middle of Lake Superior sits Isle Royale, one of the least-visited national parks in the country. It’s so remote that it had neither moose nor wolves for most of its history. So how did they get there? They crossed the water.

The moose arrived first, around the early 1900s — most likely swimming across from the Minnesota or Canadian mainland (moose are surprisingly strong swimmers). The wolves came later. During an especially brutal winter in the late 1940s, Lake Superior froze solid enough to form an “ice bridge” connecting the island to Ontario, roughly 15 miles away, and a small number of wolves simply trotted across.

That accidental arrival kicked off something remarkable: the Isle Royale wolf-moose study, run by Michigan Technological University, which began in 1958 and is the longest-running predator-prey study in the world. Scientists have watched the two populations rise and crash in a decades-long seesaw. The wolves once dwindled to just two highly inbred animals, prompting the National Park Service to bring in new wolves in 2018 and 2019. Michigan Tech’s 2026 Winter Study (conducted Jan. 22–March 3) counted exactly 37 wolves in three packs — a level not reached since the late 1970s — alongside just 524 moose, down from 840 two years earlier; for the first time in 68 years, researchers spotted no moose calves at all. And in a striking sign, a short-lived ice bridge formed again in early 2026, a throwback to the icy winters of decades past.