You can listen to today's Environment Report here or read an expanded version of the story below.

Wolves and moose fight for survival on Michigan's Isle Royale National Park. For more than 50 years, researchers have been closely watching them in the world’s longest-running study of predators and prey.

The number of predators on the island has been sinking fast.

The Park is a dedicated wilderness area, so managers do their best to keep it as untouched by humans as possible. But people might need to step in.

Phyllis Green is the park's superintendent. “At this point we’re concerned about the low levels of wolves on the island, but we’re also concerned about making sure the next steps we take are well-thought-out,” she says.

There are just eight wolves left on Isle Royale. This is the first year that Michigan Technological University researchers were unable to document any pups born to the wolves.

In our special series last year, we reported that Michigan Tech research professor Rolf Peterson said there could be a few reasons why the wolf population has been sinking:

The wolves are highly inbred, and Peterson says it’s unlikely that new wolves will come here on their own, because fewer ice bridges are forming in our warmer climate. There’s a shortage of the old moose that wolves like to eat. And a fatal disease called canine parvovirus could be hurting the wolves.

Here's Peterson talking to us about last year's drop in the wolf population. This decline, he said, is a "very big deal."

The Park Service is talking to experts to figure out what to do next.

Phyllis Green told me they're considering three main options:

Let the current population go extinct, and do nothing.

Let the current population go extinct and then reintroduce wolves to the island.

Attempt to genetically rescue the current population by bringing in some new wolves.

Green says although the Park Service likes to take a hands-off approach in wilderness areas, climate change is shaking things up.

"Climate change is changing landscapes across the U.S. and it's harder and harder for some animals to move. Isle Royale is classic because we are an island, and if that ice bridge isn't there, animals are not going to be able to come and go, unless they're swimmers in the summer, and that hasn't happened very often in the history of the park. So, nationally with climate change, the Park Service has got to look at where do we hang onto species? How do we support what's going on long term as these changes hit parks?"

Wolves hanging on by their teeth

The Michigan Tech team just wrapped up their annual winter study of the wolves and moose of Isle Royale. This is the project's 55th year. I checked in with Rolf Peterson this week to get an update on the wolves.

I asked him how serious it is that they weren't able to find any wolf pups.

"Well, if it keeps going, that'll be the end of them. Now it may be just a temporary thing and there may be some other animal out there able to reproduce, but the handwriting is on the wall in terms of genetic viability. So this is not unexpected, but it can't be predicted either," he says.

Peterson says the wolves are probably not reproducing because of a lack of genetic viability or because the population is now so low that wolves that might breed can't find a wolf to mate with that isn't a relative.

The decline in pup "recruitment," or pups that survive to see their first winter, has been going on for five years.

He says bringing new wolves in to the island—even just a few—might work.

"Under the present circumstances, I think it would probably be a successful injection of new genes. If the population was large—20 to 30 wolves, all territorial packs—then they might kill newcomers. But now, especially with reproduction bumping along or absent, I think they'd tend to look on new wolves with some pleasure."

He says as long as there are moose on the island, it's "entirely appropriate that there be wolves there."

What do you think the Park Service should do? The managers of Isle Royale want to hear your opinions. You can email your comments and ideas here: ISRO_Wildlife@nps.gov