Photos provided by NPS/SUNY-ESF Images taken in late September 2019 from a remote camera show two pups likely born to wolf 014F in spring 2019 on Isle Royale National Park.

ISLE ROYALE — Isle Royale National Park’s efforts to rebuild a self-sustaining wolf population are bearing fruit.

Wolf pups appear to have been born on the island in 2019 and 2020, Isle Royale National Park and State University of New York-College of Environmental Sciences and Forestry (SUNY-ESF) announced Monday. The exact number of pups is not yet known.

The wolf believed to be the mother was one of a number of wolves brought to the island over the past two years as part of the park’s plan to restore the population, which had stood at two aging, closely related wolves.

“The biggest thing is it tells us the translocated wolves have figured out their new life on Isle Royale, so much so they’ve decided they’re going to reproduce and have pups,” said Mark Romanski, NPS biologist and wolf introduction program coordinator at the park. “…It’s great news to have this indication of pups being born, and wolves doing what wolves do.”

Since 2018, 19 wolves have been captured in Michigan, Minnesota and Ontario and brought to the island. Estimates put the wolf population on the island at up to 14 in April.

Eight wolves have died on the island since the effort began, with the primary cause being aggression between wolves.

GPS data from female wolf 014F, which had been brought from Michpicoten Island, Ontario, suggested denning in spring 2019. Images taken by a remote camera that September indicated the wolf had given birth to two pups. Researchers at Michigan Technological University spotted what appears to be an additional pup in March.

While 014F is believed to have been pregnant when she was brought to the island, researchers have also spotted pups conceived and birthed on Isle Royale.

Data also indicates 001F, the first wolf to be moved to the island, had cubs this year. GPS readings could not be obtained in spring, suggesting the wolf was underground. When researchers investigated the den in June, they found 18 samples of scat appearing to be from pups. The scat will be analyzed to determine how many pups there were.

Another pup captured on a remote camera in July is believed to have been born to 014F or 015F.

Pup-sized tracks and 13 pup-sized scats were found near the same location in August.

The wolves appear to have formed into two packs, judging by the two distinct birthing sites, Romanski said. Defending territory has also been a driver of wolf-on-wolf aggression behind several of the deaths, Romanski said.

“That I think is to be expected as wolves form new social groups and defend territories, and certainly a bunch of new wolves in a new area, one can certainly going to expect they’ll have a lot of contact with each other as they reproduce and defend those territories,” he said.

The NPS and research collaborator SUNY- ESF released a summary report of the introduction effort so far at globalwildlifecc.org/research/species-recovery/isle-royale-wolf-recovery.

Without wolves, park officials have said, the growing moose population would likely continue to overbrowse the island vegetation.

Looking at clusters of wolves through GPS location, researchers found 50 instances of animal kills, nearly half of which were moose. Others included beaver and snowshoe hare.

“With the numbers we’re seeing, it’s certainly indicative of the wolves being a predatory force on the moose,” Romanski said.

NPS plans called for the translocation of 20 to 30 wolves over a three- to five-year period.

Romanski said there is an ongoing discussion about whether more wolves will be brought to the island. Whether it happens — and if so, how many and from where — will be determined by looking at the wolf population, its social structure and its genetic diversity.

Romanski thanked the number of partners involved in the effort, including universities, government agencies and tribal partners.

“I’m grateful for all they have done to put wolves back on the park,” he said.