The wolves of Isle Royale National Park in Michigan are the subject of the world’s longest predator study, having been observed by scientists for 57 years. Long the only predatory species capable of keeping prey animals (like moose) on the island in check, the Isle Royale wolf population has hit an all-time low: According to researchers from Michigan Tech, just three wolves remain. By the looks of things, it may not stay that way for long.
Since 2009, the wolves’ numbers have plummeted 88% from 24 to the current three. Moose, on the other hand, appear to be flourishing in the absence of their only predator. Their numbers are estimated at 1,250, and have grown at a rate of 22% annually for the past four years. The researchers are concerned for the affects an unchecked moose population might have on the island’s vegetative ecosystem. The wolves, all but nonexistent, aren’t doing much to help.
“It’s not the presence of wolves that matters so much, it’s whether wolves are performing their ecological function,” says John Vucetich, an associate professor of wildlife ecology at Michigan Tech.
Though human influence doubtlessly plays a part in the wolves’ demise one way or another, they’re mostly victims of their own undoing. Inbreeding appears to have been a problem among the small population, as evidenced by the third wolf on the island. It’s a pup estimated to be around nine months old, likely the offspring of the other two. It’s deformed, with a cinched waist, hunched posture and a crooked tail. The researchers estimate it might not last another year. Even if it did, two healthy wolves with a gimpy sidekick do not make for a formidable moose-hunting party.
Another issue appears to be voluntary flight. Ice bridges form in the winter between the island and the mainland, and over the years Isle Royale wolves have left, never to return. It’s possible that genetic diversity from outside wolves could have strengthened the population, but they don’t appear interested: Scientists observed two outside wolves on the island, only for them to leave a week later. Isle Royale, it appears, doesn’t offer much to non-indigenous wolves, even with all of those moose walking around.
“There is now a good chance that it is too late to conduct genetic rescue,” says Vucetich.
The only two options for conservationists are to attempt to introduce new wolves to the island, or do nothing and allow nature to take its course. There’s no guarantee that the two remaining wolves would interbreed with outsiders, particularly if they’re already a mating pair. Seeing as how the Isle Royale wolves are not a unique species or subspecies, it’s less a case of extinction and more an instance of wolves moving to where the action is while others breed themselves out.
In the mean time, scientists aren’t sure what to do with all of those moose, who are approaching their highest populations since 1996.
“At that time the moose population had considerable impact on forest vegetation,” Vucetich and Peterson write in the Winter Study annual report. “Concerns remain that the upcoming increase in moose abundance will result in long-term damage to the health of Isle Royale’s vegetative community.”