This male wolf was successfully transported to Isle Royale National Park this week. A female captured Thursday died in captivity/USFWS, Courtney Celley

A female wolf captured with intent to be released at Isle Royale National Park died before it could be set free. Officials didn't identify the cause of death, but said they were altering field procedures for handling wolves captured for the park's wolf recovery program.

In a brief release Friday evening, park staff said the animal was captured on Thursday, given a quick exam in the field by wildlife biologists, and "deemed fit for transportation." While the wolf was sedated and taken to a holding facility for a more detailed exam, her condition deteriorated and she died. The wolf was transported to the University of Minnesota Veterinary Diagnostic Lab for necropsy and diagnostic evaluation Friday.

"Per the implementation plan, the team and partners immediately reviewed protocols. Adjustments were made to the protocols including the length of time a captured wolf is kept in the field prior to transport, and the sedation procedures used to lower stress during transportation," the release said.

Isle Royale officials could not immediately be reached Friday evening to say how long the wolf was sedated and kept in the field.

On Tuesday, four wolves were captured from different pack territories on the Grand Portage Indian Reservation in northeastern Minnesota. Two of the wolves were deemed too young to be part of the recovery program and set free, while two others -- a 4-year-old female and 5-year-old male -- were successfully released on the island in northern Lake Superior.

Under a 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. This fall they hope to move six wolves to the island.

Chronic inbreeding has impacted the health of the island's wolf population. 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.

Isle Royale wolves have been in decline for more than a decade. 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 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.

Late this spring biologists said just two aging wolves remained at Isle Royale, while the park's moose population had swelled to nearly 1,500. Balsam fir forests on Isle Royale are vanishing in large part due to heavy browsing by moose, according to this year's ecological study of the two species at Isle Royale. Without intervention, the biologists who wrote the study -- Rolf O. Peterson, John A. Vucetich, and Sarah R. Hoy -- predicted the park's wolves would vanish and the island ecosystem will suffer.