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Isle Royale wolf population down to 3, National Park Service considers next steps

May 14, 2015

The wolf population on Isle Royale has been dropping for some time.

There were nine animals last year. In their latest winter study report, researchers on Isle Royale only spotted the three wolves pictured above on the entire island.

Isle Royale has been home to the longest running predator-prey study in the world -- researchers have been studying how wolves prey on moose here since 1958.

The researchers have seen the wolf population ebb and flow, but they haven't seen anything like this in all that time.

Since 2009, the wolf population on Isle Royale in Lake Superior has dropped by almost 90%. 

View from Lookout Louise, Isle Royale National Park, Rock Harbor, Michigan.
Credit Joe Ross / Flickr

Researchers say the relatively small island, it's 207 square miles in size, has had on average between 18 to 27 wolves organized into three packs. But they've been on the decline for the last 15 years.

The researchers say the wolves are highly inbred and they suspect the inbreeding is leading to their demise.

John Vucetich heads up the wolf-moose study on Isle Royale. He explains how migrating wolves have helped the population in the past.

"A wolf would come to the island and become part of the population, and when that happened it brought with it genes that would reinvigorate the population," says Vucetich.

"For many years, that's what kept the population going and with each passing decade, the climate warms and those ice bridges become relatively rare things."

Two ice bridges in the last two years

The past two winters have been cold and two ice bridges did form. Two years ago, a wolf left the island and was later shot and killed.

Two wolves that visited Isle Royale for six days in late February.
Credit Rolf Peterson and John Vucetich / Isle Royale Wolf-Moose Study

This past winter, two new wolves crossed the ice and came to the island, but they didn’t stay.

Vucetich says it’s hard to determine why.

"The decisions that dispersing wolves make are complicated," he says.

"They're looking for mates and they're looking for territory, and so these dispersing wolves, they either didn't know that there are Isle Royale wolves present or they knew they were present but decided that they wouldn't represent worthy mates."

So two ice bridges in two years hasn't helped the population. 

National Park Service weighing options

Since this is a national park, it's up to the park service to decide what to do. The decision on what to do next is up to one person, and that’s Park Superintendent Phyllis Green.

"From the standpoint of the National Park Service, we are always interested in the results of the winter study report," Green says.

The report's finding of just three wolves left doesn't seem to alarm her.

"It is not at this point in time causing us to take any immediate action, but we are gathering data for moving into our planning process," Green says.

The wolf-moose researchers have been disappointed by the lack of action on the part of the Park Service.

"I think it's a bit of a shame because it's a time-sensitive decision and they've known about the problem for a long time and they should make a decision, rather than just kind of making a de facto decision by punting or delaying," says Vucetich.

Green says the park is a wilderness area, and over time, species come and go from the island, so there's a lot for them to consider when deciding whether to step in or not.

With regard to the wolves, Green says they do expect to announce a formal planning process for what to do next, and she says there will be a lot of options on the table. They could range from doing nothing, to bringing new wolves to the island. And if they decide to bring in new wolves, they'll plan on ways to manage that reintroduction.

The wolf-moose researchers feel it's too late to rescue the current wolf population - "genetic rescue," as it's called. But Green doesn't feel that way. She thinks it's still possible with the current two animals being a breeding pair, but she says she does realize the "clock is ticking" for this option.

Moose population control

The researchers say, regardless of whether or not the current population is saved, wolves are critical for managing the moose population on Isle Royale. Without wolves, they say the moose population could reach levels that are not good for the island's ecosystem.

But Green doesn’t seem to feel the urgency. She says we’ve seen boom and bust cycles with the moose before.

"They climbed to problematic levels twice," Green says, "once with wolves, and once without wolves, so I think we still have time to be thoughtful on the moose side of the equation."

How long will it be before we see the Park Service make a decision?

Green says they will publish a notice to move forward with the planning process in the next month or two.

How quickly they get to a decision really depends on how that review process goes.

Green says they consider everything from what the public wants, what the scientists tell them, and what the rules and regulations are for managing a national park that is a wilderness area.

In the past, managing wilderness areas has often meant taking a more hands-off approach.