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Isle Royale out of balance: The wolf-moose dilemma

Moose population has exploded while only two wolves remain on the island

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    THE BLADE PHOTO ILLUSTRATION/JEFF BASTING
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  • Isle-royale-wolves-inbreeding

    Inbreeding has caused the drastic decline in the wolf population on the island, and the outlook is grim.

    MICHIGAN TECH

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    Isle Royale

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    John Vucetich, a Michigan Tech professor, said the situation has reached a crisis point and requires a 'substantive response.'

    MICHIGAN TECH

  • Predator-and-Prey-WOLVES-AND-MOOSE

    When wolves are present in sufficient numbers on the island, they hunt in packs and chase down moose. That allows them to kill a moose that is 10 times the size of an adult wolf.

    MICHIGAN TECH

ISLE ROYALE, Mich. — This long, forested stretch of rock protruding from the waters of Lake Superior is one of the least-visited national parks, since it is a remote and rugged patch of wilderness that is both protected and isolated by a wide, natural moat that makes it accessible only by boat or seaplane.

And it is that curtain of deep, frigid water that has allowed Isle Royale to serve as a unique Petri dish for the study of the predator-prey relationship between its moose and wolves.

VISITING ISLE ROYALE

■ Park is open April 16 through Oct. 31; National Park entrance fee: $7/day

■ Ferry service available from Houghton or Copper Harbor, Mich., and from Grand Portage, Minn. Seaplane service from Houghton.

■ Ferry service starts in May and runs into September or October. One-way rates vary from $220 for seaplane to $71-$136 for ferry service.

■ Schedules and rates at nps.gov/isro

ISLE ROYALE FACTS

■ Largest island in Lake Superior at 209 square miles

■ Accessible only by boat or boat plane

■ No private vehicles allowed but park has more than 165 miles of hiking trails

■ Surrounded by 400 smaller islands 

■ Sees fewer visitors in a year than Yellowstone has in a single day

Moose likely arrived here about 100 years ago by swimming the 20 or so miles that separate the island from Ontario and Minnesota. Wolves arrived in the 1940s by crossing the ice.

For nearly 60 years, biologists have closely monitored the two populations in the longest-running predator-prey study in the world. With no bears or hunters present, wolves are the only limiting factor on the resident moose short of disease or starvation.

Moose numbers saw a high of around 2,500 about two decades ago, while the wolf population peaked at 50 animals around 1980. The wolf numbers crashed to just 14 individuals a short time later due to canine parvovirus, passed along when a park visitor broke the strict rules and brought a dog to the island.

The wolves recovered to about two dozen by 2008, but their numbers have steadily declined, due primarily to extensive inbreeding. Now there are just two wolves left on the island — a father and daughter — while the moose population has exploded to more than 1,300 animals, and as a result the plant life and habitat are being degraded.

The National Park Service has presented four options to address the issue: one calls for no action, and three others seek varying degrees of intervention. In 2012, research professor Rolf Peterson from Michigan Tech saw the island’s wolves on the path to extinction, so he urged use of a genetic rescue plan that would bring mainland wolves to Isle Royale to invigorate the genetic pool. No action was taken, and now the situation is much worse.

“The moose population is doubling every three or four years,” he said recently, warning of the dramatic impact on the ecosystem as the moose heavily browse deteriorating stands of balsam fir.

Mr. Peterson and John Vucetich, a Michigan Tech professor who leads the research project, continue to advocate for the introduction of new wolves that would be trapped elsewhere on the mainland and brought to Isle Royale. Mr. Vucetich said the situation has reached a crisis point and requires a “substantive response.”

“The presence of wolves alone is not as important as their ecosystem function,” Mr. Vucetich said. “As long as there are moose on the island, predators are needed to check the population.”

The park service historically avoids intervention in most cases, meaning the only rescue would come from other wolves crossing the ice bridge and establishing themselves on the island, which has not happened in 20 years. Culling moose was considered but not deemed to be a feasible option.

“It is more timely to focus our energy on — should we keep this apex predator on the island, or not,” Isle Royale National Park Superintendent Phyllis Green told NPR in 2016.

Wolf biologist David Mech with the U.S. Geological Survey recommends a cautious approach and rare intervention “based on the fact that the present wolf population required no intervention for more than 60 years.”

The National Park Service is taking public comment on the wolf issue on Isle Royale through March 15 at the parkplanning. nps.gov/isrowolves website.

GRAY WOLF Canis lupus

■ Wolves are the largest member of the Canid family, which includes coyotes, foxes, and wild dogs.

■ Adult wolves average about 65 pounds.

■ Wolves are native to the rest of Michigan but are believed to have first reached Isle Royale from Ontario via the ice about 70 years ago.

■ Wolves hunt in a social unit or pack and often travel 30 miles a day in pursuit of prey.

■ Current wolf population on Isle Royale: 2 adults.

■ Wolves will often travel 30 miles a day in pursuit of prey.

■ Wolves hunt into the wind and first detect moose by smell. They can smell a moose from 300 yards away.

■ Isle Royale wolves hit a all-time peak in 1980 with 50 wolves in five packs.

■ Wolves consume most of their prey, leaving only the rumen contents, larger bones, and some hair.

■ Lifespan: wolves can live 8-14 years in the wild

Sources: MDNR, NPS, USFWS

 

MOOSE Alces alces

■ Moose are the largest member of the Cervidae family, which includes deer, elk, caribou, and reindeer.

■ Adult males (bulls) average close to 1,000 pounds, while females (cows) average about 750 pounds.

■ Moose are native to most of Michigan but have been gone from the Lower Peninsula for more than 120 years.

■ Moose can live 20 years or more in the wild.

■ Moose are strong swimmers and are believed to have reached Isle Royale about 100 years ago.

■ Peak moose population on Isle Royale: nearly 2,500 animals (1996).

■ Current moose population on Isle Royale: more than 1,300.

■ An adult moose will consume 30-40 pounds of vegetation a day.

■ Moose are primarily solitary animals, although calves will stay with their mothers for a year

Sources: MDNR, USFWS, National Wildlife Federation

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