The good news is solid ice formed between Isle Royale and the North Shore of Lake Superior, opening up a route for new wolves to walk out to the big island.

The bad news is, so far, the only wolf to make the trip has gone the other way - back to the mainland.

Isle Royale National Park officials on Wednesday reported that a single female wolf, one of three transplanted to the island for the Grand Portage Reservation in October, made its way onto the ice and back to shore in Ontario. That leaves just two transplanted wolves and two native wolves left on the island.

Wolves originally made their way to the island crossing the ice and, over many years, built up a solid population, feeding on the wealth of moose on Isle Royale. But in recent years, with fewer ice bridges forming during more frequent warmer winters, no new wolves arrived. The wolves that remained became inbred and genetically defective, leading to their numbers crashing over the last decade.

With only two wolves left, unable to successfully mate, the Park Service last year began an effort to bring more wolves to the island. But at least one of those wolves apparently didn't like its new home. The bolting female ended up on the North Shore just across the Pigeon River from Minnesota, not far from where it was trapped to be brought to the island.

The movement was confirmed with radio telemetry and GPS tracking, both by Park Service and Michigan Technological University wildlife biologists.

It was yet another setback in the island's wolf restocking effort. Last fall weather and other issues hampered trapping and relocation efforts. In recent weeks extreme cold weather has stalled efforts to bring six new wolves to Isle Royale from Ontario's Michipicoten Island in eastern Lake Superior.

"I was excited to see locations after not seeing anything for five days. But that excitement quickly gave way to disappointment as my eyes followed the track that led away from Isle Royale. I knew this could happen, but of course you always hope for the best," said Mark Romanski, Isle Royale National Park's chief of natural resources project leader for the wolf reintroduction effort.

Romaski said wildlife experts knew the wolves might try to make their way home, citing research by Minnesota wolf biologist Dave Mech that found relocated wolves released within 80 miles of their original range often will try to return.

The 45-mile-long, 143,000-acre Isle Royale archipelago is about 14 miles off Minnesota's North Shore. It's mostly dedicated as federal wilderness.

Wolves are relatively new to the island, having crossed the ice in the 1940s. Their numbers reached a high of 50 in 1980. Wolf numbers on the island crashed from 24 as recently as 2009 to just a 7-year-old female and 9-year-old male now. Moose came to the island much earlier in the 1900s, peaking at 2,445 in 1995 and hitting bottom at just 385 in 2007. In their annual survey last winter, scientists estimated the moose herd had grown to about 1,600 on the island.

Michipicoten Island has ample wolves that crossed over ice in recent years to feed on the island's caribou herd. The wolves decimated caribou there and now have little to eat until another ice bridge forms to get back to the mainland.

Phyllis Green, superintendent of the park, said that the setback won't affect the wolf reintroduction effort planned over the next three years. Efforts to bring more wolves to the island from Canada and Michigan will continue, she said.

The nonprofit National Parks of Lake Superior Foundation has made more than $100,000 available this winter to both continue the wolf relocation effort and continue the more than half-century research effort by Michigan Tech scientists to study the island's moose and wolves, even if the federal government shuts down again.