ISLE ROYALE, Mich. — Another two Minnesota wolves have been moved to Isle Royale in recent days as the National Park Service moves to establish a viable pack of predators on the largest island in Lake Superior.

The wolves, both females trapped on the Grand Portage Chippewa Reservation at the tip of Minnesota’s Arrowhead, joined two other Minnesota wolves brought to the island last week.

This week’s transfers took different transportation modes: The first took a boat ride, and the second was flown to the island.

The wolf released on Tuesday weighs approximately 70 pounds and shows signs of having had pups in the past. Veterinarians estimated she is five years old. Once on the island, the wolf waited in the crate for less than an hour before walking away to her new home. Two days later, she was seen on one of the park’s remote wildlife cameras.

On Thursday, the other female wolf was flown on a U.S. Fish and Wildlife Service airplane to the island and carried by park staff over a hiking trail to her release site.

So far, all four new wolves appear to be doing all right. A fifth wolf trapped in Minnesota died before it could be released on the island.

The Park Service hopes to add at least two more wolves from Minnesota or Michigan in coming days, with a goal of at least 20 and up to 30 new wolves moved to the island over the next three years. Half the wolves will be male and half female. They will be spaced out on their new island home to avoid inter-pack fighting. All will be fitted with GPS collars to keep track of their progress or problems.

Fall is considered the best time to move wolves because there are few, if any, people on the island over the winter, with the park closed to the public after Oct. 31 each year.

Wolf numbers on the island crashed from 24 as recently as 2009 to just a pair earlier this year, a 7-year-old female and 9-year-old male, as inbreeding spurred genetic defects that have crippled the wolves’ ability to survive and reproduce.