Moose populations are still going wild on Isle Royale, but wildlife managers hope moving some additional wolves in will help restore some balance.
Michigan Technological University’s latest annual winter study of the animals’ Isle Royale populations found there are now more than 2,000 moose there, in comparison to just 15 wolves, most of them recent transplants via human intervention.
As of mid-2018, just one lone pair of wolves—a father-daughter duo who are also half-siblings—remained on Isle Royale. That’s when the National Park Service began shipping in new wolves from several locations in an effort to jumpstart the wolf population and restore the animals’ predator-prey relationship with moose.
The hope is that the new wolves will start to establish themselves there and begin reproducing, says Michigan Tech research professor and study co-author Rolf Peterson.
“There are now enough wolves at Isle Royale, both males and females in just about equal numbers, so that somebody is going to reproduce by next year,” Peterson says.
Peterson says the wolf population has dwindled due to inbreeding, as fewer animals from the mainland have been able to reach the island via ice bridges in the winter. Meanwhile, the moose population has shot up, putting the island’s native forests in jeopardy.
“Moose continue to increase and that’s a concern because they eat so much. And they can really destroy the integrity of the forest as we know it,” Peterson says. “Most trees over a major portion of Isle Royale, the western half, are unable to grow into real trees.”
The annual winter study, now in its 60th year, tracks fluctuations of the Isle Royale’s wolf-moose populations. Peterson says it has three objectives: to count the number of wolves, estimate the number of moose, and figure out how many of those moose were killed by wolves.
“The newly arrived wolves have been on Isle Royale for too brief a time for them to have significantly influenced the demography of the moose population,” the study’s authors wrote. “The impact of the moose population on vegetation is increasingly apparent. In February 2019, 20 female moose were outfitted with GPS radio collars as part of a project to better understand how the arrival of new wolves will impact moose demography and behavior.”
Peterson says a predation rate of 10-15% would be expected in a more balanced ecosystem and “we’re nowhere near that now.” It will take at least a couple solid years of wolves reproducing to start to swing the balance, he says.
Meanwhile, “the wolves have to shop around and figure out their own lives,” Peterson says. “The first wolves to reproduce will ultimately be the winners in the territorial contest, I think. And that should unfold in the next year or so.”