One of the world’s longest-running wildlife field studies has fallen prey to the coronavirus pandemic and the US-Canada border closure.

Since 1959, a US research team has spent most of the winter observing the interplay between wolves and moose at Michigan’s Isle Royale National Park in Lake Superior. But this year’s mission has been scrapped to protect the scientists and support personnel from possible exposure to the virus.

Experts from several universities, the US park service and the Grand Portage Band of Lake Superior Chippewa had planned to assess how an effort to rebuild the wolf population is affecting the ecosystem during the park’s winter closure, Nov. 1-April 15.

However, researchers would have had to use a single cabin, which wouldn’t allow for social distancing. Also factoring into the decision to cancel the expedition, says park superintendent Denice Swanke, is the border closure between the US and Canada and a shortage of flight resources to bring supplies.

The park service and partners will instead try to document wolf population changes this summer using remote cameras and other techniques, says Swanke. But they won’t have the benefit of aerial observations that can be done only during winter, when the animals are easier to spot.

“There will just be a hole in the data that nothing can be done about,” says John Vucetich of Michigan Technological University, one of the biologists who have produced annual reports about the wolves and moose that roam the island park, as well as its other wildlife and vegetation.

Wolves are believed to have crossed ice bridges from the mainland to the island in the mid-20th century. They established packs and helped keep the moose from overpopulating their habitat.

When inbreeding all but wiped out the wolves in recent years, officials began airlifting in others from the US and Canadian mainland.

The most recent count last year put their numbers at 12 to 14. The moose herd was estimated to number 1,876.