Wildlife

Three wolves on an island: these are not good odds for long-term survival.

The wolves of Isle Royale National Park – an island on Lake Superior – constitute one of the most iconic predator populations in the world.

And according to latest reports, only three of them remain.

Eighteen months ago, I wrote an essay on the fate of Isle Royale’s wolves, pondering whether new wolves should be introduced to bolster a population that then stood at ten. The piece was one of the most controversial we’ve published on Cool Green Science.

Since then, the news for the wolves has only gotten worse.

According to ecologists at Michigan Tech, the population now includes a male, a female and a 9-month old pup in deteriorating condition. And that’s it.

What does the future hold? Three wolves is not a viable population. But the larger conservation issues – whether wolves should be reintroduced, how moose will be managed – remain for conservationists to decide.

Here’s the issue in a nutshell:

The wolves arrived on Isle Royale in the late 1940s, likely via an ice bridge. The dynamics of moose and wolves on the island became the subject of the longest running predator-prey study on earth.

In the 1980s, a virus introduced by a visitor’s sick pet decimated the wolf population. It recovered, but now inbreeding has brought the population to the brink.

Due to climate change, there were fears that new wolves would not be able to recolonize the island via an ice bridge, because ice bridges occur infrequently in warming winters.

This winter was actually a cold one for Lake Superior, and an ice bridge formed. Two wolves indeed ventured to the island – but they quickly left. Unfortunately, they didn’t breed with the existing wolves, either.

What to do next raises all sorts of interesting conservation science dilemmas.

As I noted in my original piece, in many ways what has happened to wolves mirrors what often happens to wildlife species on islands: they come and go. This is what ecologists call island biogeography.

In the 1800s, there were not wolves on the island. Nor were there moose. Historically, there would have been lynx and caribou – both no longer present.

New species continue to arrive on the island, including a bat and several amphibians.

But, as critics of my essay correctly pointed out, this is not a case of “natural” evolution on the island. The caribou and lynx disappeared due to human activity. Wolves were dealt a huge blow from an introduced virus. Human-caused climate change influences the ability of new mammals to reach Isle Royale.

“One must use the word, ‘naturally’, carefully these days,” says Rolf Peterson, the longest-serving director of wolf-moose studies on Isle Royale. “The human imprint is written all over the dynamics of this wolf population in recent decades.”

Peterson and others also emphasize that one of the important considerations is the cost of losing an apex predator. A hyper-abundant moose population could cost more to manage than the costs associated with reintroducing wolves.

The moose population has been increasing at a rate of 22 percent per year for the past four years. That could cause significant ecological damage to the national park. And it’s certainly due to the absence of wolves.

Should wolves be reintroduced immediately? Or should biologists wait until the population disappears and reintroduce an entirely new pack? The National Park Service is researching options, but that decision could take years.

What if the wolf population follows this pattern – flourishing for a bit and then dwindling after 40 or 50 years? Is that a good use of conservation resources? How many wolves would be necessary to avoid inbreeding?

Ultimately, I concede that Peterson is right: “letting nature take its course” on Isle Royale is, at this point, impossible. The heavy hand of humanity has been felt there for a long time, and will continue to do so in the future.

But that fact still does not direct conservationists what to do next. What do you think? What should the future of Isle Royale look like?