Three more Michigan wolves were delivered to Isle Royale in recent weeks to bring the island’s wolf population to 17, nine males and eight females, up from just two wolves a year ago.

The latest three wolves came from the Upper Peninsula, as was planned as part of the National Park Service's ongoing efforts to restore a viable, self-sustainable wolf population to the island.

The last two native Isle Royale wolves, a father and daughter, have been hanging on but are unable to successfully mate.

A fourth Michigan wolf brought to the island this month was quickly found dead after being released. The cause of death has not yet been determined.

In addition to Upper Peninsula wolves, the other new wolves brought to the island over the last year came from the Grand Portage Indian Reservation in Minnesota and from an Ontario island on Lake Superior. The three new wolves are expected to be the last wolf relocations for this year, but the relocation effort is expected to continue until the island wolf population hits about 30. If the existing wolves produce many pups that survive, fewer relocations will be needed in the next couple of years, Park Service officials note.

Isle Royale is Lake Superior's largest island. The National Park is located about 14 miles off Minnesota’s North Shore. It has a large and potentially overcrowded population of moose, and wolves are the only predator on the island.