Scientists look for moose clues
Outdoors: Scientists look for moose clues
By Glen Schmitt Times outdoors writer
Published: April 01. 2007
GRAND RAPIDS � The moose population in northwestern Minnesota numbered in the thousands as recently as 20 years ago.
Less than 100 remain today in a narrow strip of land from Thief River Falls to the Canadian border.
In the northeast part of the state, aerial surveys conducted by wildlife officials this past winter also showed a decline in moose numbers. Last year, 8,400 moose were estimated in this region, but this year that total dropped 23 percent � down to 6,500 moose.
The reason for Minnesota's declining moose population remains a mystery. Up to this point, it's been very difficult to pinpoint one specific cause for the mortality, especially in the northeast.
Recent studies suggest that climate change, parasites and malnutrition are to blame for the decline in moose numbers throughout the northwest part of the state. Moose in Minnesota are at the southern fringe of their North American range.
The study, which began in 1995, documented temperature increases and longer growing seasons in the northwest. Moose prefer temperatures below 70 degrees. Otherwise, they burn more energy to stay cool and ultimately become more susceptible to parasites and malnutrition.
"Moose expend energy to regulate their temperature in the warmer months by panting," said Mark Lenarz, DNR wildlife researcher. "If they're panting, they don't eat as much and that saps their energy reserves."
Others believe warm weather isn't the only cause in the demise of the northwest population.
While most wildlife experts know parasites such as brain worms and liver flukes take their toll on moose, other unidentifiable parasites may exist. Finding out what those are and how to combat them is the frustrating part.
"We continue to work with scientists from around the world to determine what might be causing mortality in these moose," Lenarz said. "At this point, I don't think it's one disease or one parasite, but we don't know."
In the northeast, the decline in moose numbers during this year's survey is a concern for Lenarz, but not a major surprise. Results from a five-year study in this region indicate that the non-hunting mortality rate for moose is higher in northeastern Minnesota than anywhere in the United States.
The program involved fitting 116 moose with radio-collars. Over the past five years of the study, 80 of those animals have died. Non-hunting mortality of these moose has averaged about 22 percent, although the rate in the northeast was 34 percent this past year.
Lenarz said non-hunting mortality elsewhere in North America is usually 8 to 12 percent annually. While he knows a few of the radio-collared moose have been killed by hunters, wolves or in collisions with motor vehicles, the majority of moose deaths remain a mystery.
"They appear to have died from some form of parasite or disease and you typically don't see things such as liver flukes in the northeast," he said. "We've tested for all the diseases and parasites known to kill moose, yet the cause in most cases remains unclear."
The winter survey results also showed fewer calves. Lenarz pointed out that calf reproduction by cows appears to be at its lowest point in 20 years. Those with twin calves also were significantly lower than past years.
With no specific answers for declining adult and young moose, some big game experts believe it might be time to look at other variables in future years. Habitat improvement and reducing hunting opportunities are two options that will be given a serious look in the northeast.
If the downward moose population trend continues in the northeast, closing the hunting season might be another option. But that possibility is many years down the road in Lenarz's estimation � if it ever happens at all.
He says that hunting harvest likely accounts for fewer dead moose than those killed by wolves and vehicles each year. Lenarz made it perfectly clear that hunting is not driving the moose into extinction.
During the 2006 hunting season, licensed moose hunters harvested 133 bulls and 28 cows. The success rate was 60 percent, with 279 permits available in the northeast part of the state.
Some changes in the 2007 moose season have already been made as a result of the decline in moose numbers throughout the northeast. The changes are precautionary measures, according to Lou Cornicelli, DNR big game program coordinator.
In the past, hunters who drew one of the state's once-in-a-lifetime moose permits could harvest either a bull or cow. This season, licensed hunters may harvest only antlered moose.
"While hunting harvest is only a minor part of overall moose mortality, DNR biologists feel that restricting cow harvest is a prudent measure," Cornicelli said. "Especially given the unexplained mortality in northeastern Minnesota."
Other changes for the 2007 moose season include:
� Moose zones have been reconfigured to better reflect the Boundary Waters Canoe Area Wilderness (BWCAW) boundaries.
The new zones will allow hunters to clearly identify their zone of interest before applying for a permit. Hunters are encouraged to consult the moose application guide, available where licenses are sold.
� The application deadline has been moved up to Friday, May 4. This change, which will allow the DNR to inform applicants about six weeks earlier than in past years, will give hunters more time to prepare.
For now, the DNR will continue to work with scientists to try and figure out what's behind the continuous decline of the state's moose population. In the northeast and northwest, those answers appear difficult to define.
"The moose is the icon of northern Minnesota," Lenarz said. "To see their numbers steadily decline is disturbing."