When teams from the U.S. and Canada worked together last week to net-trap four wolves in Ontario and fly them to Michigan's remote Isle Royale, they were working against the clock.

The long-planned catch-and-relocate effort - part of the National Park Service's plan to boost the number of wolves on the island wilderness now teeming with moose - had been hemmed in for weeks. Organizers had overcome bouts of severe weather that kept their planes grounded. And they'd weathered a drawn-out U.S. federal government shutdown that put a lid on any activity at Isle Royale, which is also a national park.

Finally, they were racing against biology. They needed to get the Canadian wolves settled into their new home before the early spring breeding season. 

The two teams released photos this week, showing the details of the capture and release of the four wolves. One is a 65-pound female. The other three are large males, all in the 90-pound range. Sturdy, large-muscled wolves thought to be just the right predator to start thinning the island's burgeoning moose population.

Two males - include a pack alpha - were captured with net guns fired from a helicopter flying low over Canada's Michipicoten Island Provincial Park, which sits in northeastern Lake Superior. A female and a male were caught in similar fashion on the mainland, near Wawa, Ontario.

The four new wolves join two other female wolves trapped and relocated to Isle Royale last fall from tribal lands in Minnesota, and the island's longtime male and female pairwho for years had been the only predators of their kind there.

The wolf-restocking project has seen some early losses. A third female wolf from Minnesota used an ice bridge to cross back to the mainland at the end of January. A male from Minnesota was found dead on the island after several weeks. Another female wolf trapped in Minnesota died before she could be brought to Isle Royale.

The goal is to increase the wolf population by up to 30 over the next few years.

For now, Isle Royale's wolf numbers will stand at eight.

There are no plans to relocate more this winter, park spokeswoman Liz Valencia said, according to the Associated Press.

Currently, 93 percent of Lake Superior is ice-covered. Researchers know there's a chance any of the new wolves could decide to try to cross back to the mainland.

"That's part of the gamble," she  said. "But these are farther from their home territory than the wolves  last fall. So it's less likely, based on science, that they'll try to  return — but not impossible."

The photographs are being shared here courtesy of the National Park Service and the  Ontario Ministry of Natural Resources and Forestry.

A helicopter was used to locate and net-trap the wolves.

A helicopter touches down after a successful wolf catch.