Isle Royale wolf, moose populations increase

Moose and wolves on Isle Royale have been confounding researchers for a half century now, and 2008 is no exception. A new survey shows that the populations of both animals increased over the past year on Lake Superior's largest island. The just-t...

Moose and wolves on Isle Royale have been confounding researchers for a half century now, and 2008 is no exception.

A new survey shows that the populations of both animals increased over the past year on Lake Superior's largest island.

The just-tabulated results mark the 50th anniversary of the Isle Royale wolf/moose study, considered the longest running research project of predator/prey relationships in the world.

Wolves increased from 21 in 2007 to 23 this year and grew from three to four packs.

Moose, which are more difficult to count accurately, increased from an estimated 385 in 2007 to about 650 in 2008, although much of that increase may be due to difficult counting conditions in 2007 that underestimated the population.


Researchers aren't sure whether the uptick in populations is the start of a positive trend or an anomaly before a return to declines that have marked recent years.

The wolf population is near normal while moose remain well below average. There also are very few old moose, the animals wolves like to target.

That mix can't last too long and should mean tough times for wolves as they have to work harder to get a meal, said John Vucetich, co-leader of the Isle Royale study and a professor of forestry at Michigan Technological University.

That's what happened from 2006 to 2007, when wolf numbers crashed from 30 to 21.

"We were a bit surprised that wolf numbers went up even by two. We expected them to slide again this year because there are so few moose on the island now,'' Vucetich said. "The creation of a fourth pack also is very unusual. It's only the fourth time in 50 years that's happened.''

Getting warmer

Vucetich also is surprised that moose numbers held steady or even increased considering that the summer of 2007 was among the warmest since the study began. He noted seven of the past 10 summers have been among the warmest of the last half-century.

Moose begin to feel heat stress at temperatures above 55 degrees, Vucetich said, and eventually stop eating altogether on hot summer days, leaving them with less fat to survive winter.


Meanwhile, the winter tick population exploded last year thanks to an early, warm spring and mild autumn. It was the worst infestation ever counted.

"The average moose last year lost about three-fourths of its hair. And half the moose lost 95 percent of their hair'' trying to rub ticks off, Vucetich said. "We had a lot of naked moose running around the island.''

That stress caused 2007's calf numbers to decline from an average of 15 percent of the population to just 5 percent, which wildlife biologists say is not sustainable over the long term.

Scientists won't see how many calves are born this year until later this spring.

Vucetich said repeated warm summers, which he links to global climate change, could spell a long-term decline for moose on the island, as has already occurred in parts of Minnesota. If moose decline much farther on the island, it could spell doom for the island's wolves even faster, Vucetich said.

"If moose drop much more, it's the wolves that would likely go extinct first,'' he said. "Once that happens, the few remaining moose may actually do pretty well.''

Vucetich conducts the survey with retired Michigan Tech Prof. Rolf Peterson, who has been working on the project since 1970. Durward Allen started the study in 1958.

Rollercoaster changes


Moose came to the island about 1900 and peaked at 2,445 in 1995. Last year's 385 moose were the fewest ever counted.

Wolves are relatively new to the island, crossing winter ice in 1949. Their numbers have ranged from just 11 in 1993 to a high of 50 in 1980.

Isle Royale sits about 15 miles off Grand Portage on Minnesota's North Shore.

Experts say that a perfect balance would be about 1,000 moose and 25 wolves, but they also say that what humans might consider perfect balance is almost never met in the wild. Disease can throw every other factor aside, such as when a mutant strain of canine parvorvirus was brought to the island by a pet dog and almost wiped out wolves in the 1980s.

"Saying things are out of balance has sort of a negative connotation,'' Vucetich said. "Really, what we've learned after 50 years, is that the normal state of affairs is dynamic variation. It's ever-changing ... Balance is never really met.''

Vucetich said he hopes the study will continue at least another half century -- if there are moose and wolves on the island to study.

The study is more than counting animals. It documents the effects of climate and weather, parasites, disease, forest changes and time as the predators and prey do their dance of survival. The study also shows the interaction with foxes and ravens, and how forest ecology is affected by the predator/prey balance.

"Isle Royale is a fairly simple system, yet it is still so complicated that it surprises us almost every year,'' said Peterson, who started working on the study in 1970 and has been leading it since 1975. "People want to predict the future with wildlife and [nature] and that's just laughable. We can't predict it at all.''

Adrian Wydeven, wolf biologist for the Wisconsin Department of Natural Resources, said the Isle Royale study highlights the value of long-term research.

"A lot of us got our interest in wolves watching what was going on at Isle Royale when we didn't have any wolves,'' Wydeven said. "The real value of their research has been showing how much change there is over the years ... If they would have ended that research at the end of any of [the] decades, they would have had vastly different conclusions. I hope they keep it going another 50 years.''

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at
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