DULUTH - Is climate change killing off Minnesota's moose?
That appears to be the case, according to scientists and wildlife managers meeting here to talk about the dramatic decline in the state's moose population in recent decades. State wildlife biologists estimate the population has dropped 25 to 50 percent in 20 years, with a near-collapse in northwest Minnesota, now estimated to have fewer than 100 moose, down from 4,000 in the mid-1980s.
They said that while disease, parasites, predation and other factors all contribute to moose mortality in northern Minnesota -- on the extreme southern fringe of this historic moose range -- heat stress from a documented rise in temperatures appears to be the root cause of the decline.
At stake, beyond the animals themselves, is their iconic status as a northern Minnesota symbol and tourist attraction. One needed only cross the street from the hotel hosting the Minnesota Moose Summit Monday to see it: In the Duluth Pack store with its patented symbol -- a bull moose. Or the moose carved from a tree trunk Outside Deco Bay Clothing. Or the sign in the window of the Animal Factory, beckoning Christmas shoppers to "stuff" a moose to take home.
Meanwhile, at the summit, which also served as the second meeting of the Minnesota Moose Advisory Committee -- a group directed by the Legislature to come up with possible responses to the decline -- there was talk of the possibility of a Minnesota without moose by 2050, if present trends continue.
"Moose are very heat-sensitive," said Prof. Rolf Peterson of Michigan Technological University, chair of the 17-member advisory committee, which plans to recommend to the DNR in June how the decline might be slowed and what new research might be needed.
"They're a 1,000-pound animal, and they're almost black," continued Peterson, who has studied the isolated moose population on Lake Superior's Isle Royale. "They don't sweat like a horse. They have no terribly effective way of getting rid of heat except by breathing faster."
The state's moose population has dropped from as many as 14,000 in the mid-1980s to an estimated 7,700 today, said Dave Schad, the DNR's division of Fish and Wildlife director. The population in northeast Minnesota has declined an estimated average 6 percent per year since 2002, according to DNR estimates based on surveys from helicopters.
Moose hunting permits have been correspondingly reduced. Since the early 1990s, a hunter lucky enough to get a permit in the DNR's annual lottery can't apply again. One possible recommendation of the advisory committee is to discontinue the hunt.
Mark Lenarz, DNR wildlife research group leader, told the group that temperature readings taken at an Ely weather station show that "over the past 48 years, average summer and winter temperatures have increased substantially." Mean midwinter temperatures in northwest Minnesota, which has fewer of the shade trees and lakes moose need to cool themselves, increased about 11 degrees from 1961 to 2001, a dramatic rise by most climate change measures.
Lenarz cited a study that found that when temperatures go above 23 in the winter and 57 in the summer, moose must expend more energy, through a faster heartbeat and more labored breathing, to maintain a healthy temperature.
No other factor examined -- not disease, parasites, starvation, deer density, hunting or predation by wolves -- correlates as reliably to the decline as does the rising temperature, Lenarz told the group.
"Because they are weakened, it predisposes them to other measures of mortality," he said, adding that because they must spend more time seeking shade and cooling off, "it takes away from the time they can actually feed."
While such a correlation has been observed, he added, "We don't have a cause and effect. ... We need to identify the specific mechanism" by which moose die of heat stress. More research is needed, he said.
Laurie Martinson, a DNR deputy commissioner, said the state is determined to find possible solutions.
"We're going to set a course that's proactive and that assures moose will be there for future generations," Martinson said before Monday's gathering, which continues today.
However, Peterson, the longtime researcher and advisory committee chair, said it may be too late.
"I don't know if we can do it," Peterson said. "We have only a few tools. ... We're not in charge of the weather. Things are just changing very quickly."
Larry Oakes • 1-800-266-9648