Northeastern Aerial Moose Survey Results

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Wildlife biologists for the Minnesota Department of Natural Resources (DNR) say a recently completed aerial survey that found 6,500 moose in northeastern Minnesota is the most accurate to date.

Until last year, the aerial survey had indicated that the moose population was stable at approximately 4,000 moose. The boost in moose surveyed in the past two years is the result of changes in survey techniques, not an actual increase in the moose population.

"We flew the survey using helicopters rather than fixed-wing aircraft, which gave observers more time to see moose," said Mark Lenarz, a DNR wildlife research biologist who coordinated the survey. "We also used a new survey technique that was pioneered in Idaho for estimating elk numbers in the pine forests of the west."

Lenarz said the new survey technique, developed for counting elk in heavily forested areas, is well suited to the coniferous forests of Minnesota's northeastern moose range. Each observation of moose is corrected based on the amount of visual obstruction where the moose is sighted.

The correction factor used in this survey was developed using radio-collared moose that are part of an ongoing study of moose population dynamics in northeastern Minnesota.

"Each year we will be able to refine this correction factor using the radio-collared moose and improve the accuracy of our population estimates," said Lenarz.

The 2004 survey, which estimated 8,500 to 11,000 moose, was unreasonably high, biologists say, due to inconsistent measurements on the amount of visual obstruction.

Aerial surveys have been conducted each year since 1960, and are based on flying transects in 36 randomly selected plots spread across the Arrowhead. This year's survey was conducted by the DNR, the 1854 Authority, and the Fond du Lac band of Lake Superior Chippewa.


For the past three years, researchers have been tracking radio-collared moose in hopes of learning why the moose population in northeastern Minnesota isn't increasing.

While this year's higher survey counts are encouraging, the study has identified non hunting moose mortality between 21 and 24 percent in the first two years of the study. This year's non-hunting mortality rate in northeastern Minnesota was 9 percent, Lenarz said. The non-hunting mortality rate for moose is generally between 8 and 12 percent elsewhere in North America.

Typically, moose that aren't harvested during hunting season are killed by various illnesses and parasites, vehicle collisions, wolves or old age (after 19 or 20 years). But during the past three years of the study, at least nine emaciated prime-aged radio collared moose have been found dead.

"We've tested for all of the diseases and parasites known to kill moose and have come up with nothing," Lenarz said. "We are continuing to collaborate with scientists around the world in our attempt to identify this unknown cause of mortality. Considering this year-to-year variability in mortality rates, it is too soon to say what the long-term trend in moose numbers will be."

The DNR will use information from the survey and the ongoing study to develop moose hunting quotas and regulations for fall. Details on the 2005 moose season will be announced in late April. The application deadline for the moose hunting license lottery is Friday, June 17.