ISLE ROYALE, MI -- After researchers found only two gray wolves appear to remain on Isle Royale, National Park Service leaders are re-examining the possibility of bringing more of the animals to the Lake Superior island.

The number of wolves on the island has dropped sharply in recent years and prompted the park's focus on whether to import them, and if so, how, the National Parks Service and The Associated Press reported Wednesday. A new public comment period is being opened.

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The National Park Service last year began studying how to manage the park's wolf and moose populations over the next 20 years. The service said Wednesday it will focus on boosting the number of wolves, the AP reported.

Wolves first made their way to Isle Royale from the mainland across ice bridges in the late 1940s. Their population has averaged in the low 20s but has declined steeply in recent years. Scientists say they're needed to keep moose numbers under control.

In their heyday in 1980, there were about 50 wolves on the island. There was a dramatic decline largely due to canine parvovirus and the population feel to 9 in January 2014 and only 3 last winter.

The figure fluctuated prior to that and at one time fell because of lower numbers of moose, which the wolves prey. In recent years, moose have been on the increase, climbing from 1,050 to 1,250 over the past two winters.

The research team that found the wolf footprints this year say they were in the slush of Lake Eva. The wolves likely spent some time exploring an active beaver pond, they said.

John Vucetich, a Michigan Tech University biologist, has advocated for the government's intervention in the wolf population.

"It's important that action be taken sooner rather than later," he said last year.

The best way to restore the island's wolf population is "bring wolves to Isle Royale as soon as possible."