LISTEN TO THE AUDIO VERSION
The loss of wolves on Isle Royale has thrown the predator-prey balance out-of-whack, leading to a population explosion of more than 1,600 moose.
By Keith Matheny
Isle Royale may be down to a lone wolf, as the federal government ponders whether it will replenish the pack on the northern Michigan Island.
Photo This screen-grab from a trail cam video was the only wolf seen on Isle Royale in September 2017 by Michigan Technological University researchers. An inbred pair of wolves were the last known to inhabit the island the past two years, but that number may be down to one.
For the past two years, a male and female wolf have held on as the last remaining pair of wolves on the more than 200 square-mile island that’s part of a national park in Lake Superior. The pair were spotted in the summer of 2016, on the motion-triggered trail camera of Michigan Technological University wolf researcher Rolf Peterson, and again in Michigan Tech’s annual winter survey of the island last January.
But the survival story appears to have taken a turn this summer.
“I wasn’t able to confirm two wolves,” Peterson said. “We did confirm one wolf with a trail camera, but we didn’t get any definitive evidence of the presence of both wolves this summer.”
The remaining pair were a father and daughter, and they were born from the same mother, making them half-siblings and highlighting the severe inbreeding that has decimated the island’s wolf pack. Past offspring by the pair were small and unhealthy, and did not survive. Peterson said that while it’s unclear from the trail cam shot, he believes the lone wolf viewed this summer is the female.
It’s more than a tear-jerker for wildlife lovers. The loss of wolves on Isle Royale has thrown the predator-prey balance there completely out-of-whack. It’s led to a population explosion to more than 1,600 moose, threatening the fir trees and other vegetation on the island with their voracious appetites, and setting up an ugly potential of mass die-offs of starving moose in years to come.
Peterson and fellow Michigan Tech researcher John Vucetich get an annual estimate every winter of the moose population, and “it’s been going up consistently over 20% every year” since the wolf pack died off, Peterson said.
“This (summer), from the calves we saw around, there’s no reason to believe it’s slowing down,” he said.
Wolves came to the island more than five decades ago by crossing a frozen Lake Superior in winter. The island’s wolf population once reached 50 wolves and averaged 25 wolves over decades before a population crash in recent years due to the physical and reproductive impacts of inbreeding. Changing weather patterns leading to fewer and smaller ice-overs of Lake Superior have made for fewer ice bridges between the island and mainland to potentially replenish the wolf population.
Peterson and Vucetich in recent years sounded warnings on the island’s dwindling wolves, and the potential repercussions. They urged the National Park Service that manages the island to institute a “genetic rescue,” stocking the island with some number of wolves from the mainland to restore breeding and build a pack again capable of taking down a good number of moose.
As the Park Service considered its dueling obligations to let nature take its course on the island, and to prevent damage to island ecosystems, the bureaucratic process dragged.
But the Park Service is nearing the release of its final plan and environmental impact statement on the Isle Royale wolf question. The draft plan, released last year, is now under consideration by the U.S. Department of the Interior, which oversees the Park Service.
“That process takes quite a long time,” said Park Service spokeswoman Alexandra Picavet.
The plan considers four options: Doing nothing, and three different scenarios for reintroducing wolves from the mainland to the island in varying numbers over different time periods. The service’s preferred alternative involves importing 20 to 30 wolves over a period of up to five years.
“I think it makes sense,” said Peterson, who served on a panel of scientists that helped answer technical questions for the Park Service as it drafted its plan.
“It puts the number of wolves back up to sort of average, and maximizes the genetic diversity.”
The public comment period on the Park Service’s plan closed in March, and public comments were incorporated into the draft final plan, Picavet said.
A notice of availability of the final plan will be published in the Federal Register, a clearinghouse for U.S. policy-making announcements, “probably right after the holidays,” she said. That will trigger a 30-day period where Park Service Regional Director Cameron Sholly considers the final plan. If it is then signed as expected, the genetic rescue plan would get under way next year, Picavet said.
If the plan gets two or three mating pairs of wolves onto the island, Mother Nature might do the rest, Peterson said.
“Within a year or so, they should all be reproducing,” he said, adding that the moose-rich, isolated habitat “is as close to Heaven as a wolf would ever find.”