Moose in Michigan's western Upper Peninsula are holding their own more than three decades after an attempt to rebuild the population with animals from Canada, although their numbers remain far lower than initially hoped, officials said Friday.
The state Department of Natural Resources said a biennial survey this winter produced an estimate of 509 moose in their primary range — a 1,400-square-mile (3,626-square-kilometer) area including parts of Marquette, Baraga and Iron counties.
That territory is believed home to 80 to 90 percent of the western Upper Peninsula's moose population. The survey didn't include areas outside the core range where biologists suspect other moose wander. Also excluded was a separate herd of fewer than 100, believed to roam the peninsula's eastern side.
The findings suggest moose in the western U.P. are increasing about 2 percent a year on average, said Russ Mason, chief of the department's Wildlife Division.
"The growth rate for this moose population is low but remains positive," Mason said in a statement. "Moose are continuing to maintain a foothold in the western Upper Peninsula, continuing to further extend the lineage of a population airlifted to the area from Canada in the mid-1980s."
Moose are native to Michigan but had all but disappeared from the state by the 20th century because of habitat loss, hunting, wolf attacks and brainworm — a disease carried by deer that doesn't harm them but is fatal for moose.
A deer drop-off in the 1970s led scientists to believe moose could thrive in the Lake Superior watershed of the Upper Peninsula. Crews relocated about 60 moose from Algonquin Provincial Park in Ontario to northwestern Marquette County in 1985 and 1987.
The goal was a population of 1,000 by the year 2000 but it hasn't come close. Hunts are not allowed because the species doesn't have a sustained growth rate of more than 3 percent, the threshold recommended by the state's Moose Hunting Advisory Council.
"We don't know how many animals we're going to be able to support in the end, but we don't think we've hit the upper limit at this point," said Terry Minzey, the DNR's Upper Peninsula regional supervisor.
At least they've rebounded from a worrisome decline in 2015, when the population hit 323, he said. Bad weather prevented a complete survey in 2017 but the population was assumed to be 420 to 470.
Crews conduct the western U.P. survey every other winter from fixed-wing aircraft.
The DNR no longer conducts field necropsies or traces particular moose with radio collars, making it harder to know what might be preventing more robust growth, Minzey said. Reproduction rates appear low, although calves appear to have a relatively good survival rate.
Wolves began returning to the area in the 1980s and now total about 660 in the Upper Peninsula. But they probably haven't significantly affected moose, Minzey said, noting the abundance of deer and other prey. Wolf attacks on moose have only about a 7 percent success rate, he said.