One of the four wolves moved by the National Park Service to Isle Royale on Lake Superior has died.
The NPS confirmed that the wolf triggered a "mortality signal" on its tracking monitor and was eventually tracked to a location on the island where its body was found.
There was no obvious cause of the wolf's death, the NPS says, and no indication that they had the died as a result of wolf-on-wolf mortality.
It's been taken to a U.S. Geological Services wildlife health lab in Madison for a necropsy.
It's not clear how long the wolf had been dead for, as its tracking collar had been malfunctioning since it was transported to the island in September.
It's the second wolf to have died as a result of the park service's effort to introduce 20-30 wolves to the island over a 5-year period, to address its overpopulation of moose.
Another wolf died in an NPS holding facility in September having been captured ahead of potential release on Isle Royale.
Since the project started, 16 wolves have been captured on the Grand Portage Chippewa reservation, seven of which have been collared and released either on Isle Royale or at the site of capture.
The NPS says that the three remaining wolves on Isle Royale are "doing well" and have been exploring the island, sometimes in close proximity to each other.
The service intends to introduce more wolves to the island in January, this time from Ontario.