One of four wolves released at Isle Royale National Park has died/NPS

One of four wolves relocated to Isle Royale National Park this fall as part of a recovery mission for the species in the park has been found dead of unknown causes, park staff announced Tuesday.

Shortly after the male wolf was released on the island its radio collar malfunctioned, transmitting a mortality signal even when remote cameras in Isle Royale showed the animal to be alive. However, late last month the collar not only sent a mortality signal, but also indicated the animal's movements were restricted to a small area. 

Isle Royale staff and partners from Grand Portage Band of Chippewa late last month traveled to the island to find the wolf and located it through telemetry and recovered the carcass. There was no obvious cause of death and no indication of wolf-on-wolf mortality, park staff said Tuesday. The animal was being transported to the U.S. Geological Services wildlife health lab in Madison, Wisconsin, for necropsy. Results are expected in December.

The four wolves captured on the Grand Portage Reservation and transported to Isle Royale had been given veterinary exams and deemed "generally" healthy before being released in the park.

Isle Royale wolves have been in decline for more than a decade, as chronic inbreeding has impacted their health. There was hope that "ice bridges" that formed between the Lake Superior island and the Canadian mainland during the winter of 2013-14 would enable wolves to arrive from Canada with new genes. But no new wolves reached the island, while one female left and was killed by a gunshot wound in February 2014 near Grand Portage National Monument.

In recent years, park managers have discussed island and wolf management with wildlife managers and geneticists from across the United States and Canada, and have received input during public meetings and from Native American tribes of the area. Those discussions have examined the question of whether wolves should be physically transported to Isle Royale, in large part due to concerns that a loss of the predators would lead to a boom in the moose population that likely would over-browse island vegetation.

Last winter's moose population was estimated at about 1,500, and biologists believe the island can support 1,100-1,200.

Since the four wolves arrived on the island this fall, park biologists have been tracking them using GPS technology, which allows daily monitoring of movement. The three remaining relocated wolves were said to be doing well and their movements were being tracked through GPS. They have occasionally been within 700 feet of each other while exploring the island.

Under the plan adopted earlier this year, up to 30 wolves are to be set free at Isle Royale over the next three years under a plan the National Park Service has settled on in a bid to bring genetic diversity back to the park's few remaining wolves. It was hoped that six wolves would be moved to the park this fall, but deteriorating weather conditions ended the operations after four animals had been released there.

However, this winter efforts will be made to capture several wolves in Ontario, Canada, and move them to the park.