Grand Rapids, Minn. – The decline in northeast Minnesota’s moose
There are an estimated 5,528 moose in that part of the state,
according to aerial survey results the DNR released this week. Last
year’s estimate was 7,593 moose, but officials say factoring in the
margin for error means there is no statistical difference between
the two years.
But there are plenty of other indications of a declining herd:
the number of calves per cow is the lowest it’s ever been; the
number of bulls per cow has declined; hunter success has declined;
and the percentage of calves seen during the survey has
“This year’s survey estimate reinforces everything else we have
been looking at with the population,” said Mark Lenarz, leader at
the DNR_Forest Wildlife Population and Research Group.
It’s the first time the results of the aerial survey have jibed
with other evidence of a declining moose herd.
Mike Schrage, a wildlife biologist for the Fond du_Lac Band of
Lake Superior Chippewa, said he’s been waiting for the population
survey to catch up with anecdotal reports of people seeing fewer
moose, and of high mortality of radio-collared moose in a study
from 2002 to 2008.
“I’m not surprised by the results; it’s almost more surprising
that we hadn’t seen them a year or two earlier,” he said.
Researchers still don’t have a firm grasp on why moose are
struggling to survive.
Climate change seems to be playing a role in that warmer
temperatures make the northeast, which already is at the southern
end of their range, less hospitable to moose. The animals can
handle cool weather, but have a tough time in the heat.
“Although we are seeing an increasing trend in summer and winter
temperatures, it’s not a straight line,” Lenarz said. “If you look
at the past 40 or 50 years, there are warm periods and cool
periods, and the past year or two have been fairly cool.
“If that pattern continues for a while, we might see the (moose)
population stabilize,” he said.
Heat causes moose to become stressed and makes them more
susceptible to diseases. Most of the deaths of collared moose in
the radio collar study were health-related, Schrage said.
Of the 150 moose collared during the study, 103 have died.
Diseases or parasites are thought to have killed most of them. Nine
moose died after being hit by cars; six were killed by wolves; and
two were hit by trains.
“We are still struggling to understand all of the causes,”
While the calf-to-cow ratio – 28 calves per 100 cows – is the
lowest it’s ever been, researchers don’t know why more calves
aren’t surviving. In a stable moose population, Lenarz would expect
to see about 60 calves per 100 cows.
It’s unclear what the predation rate on calves is, though it’s
clear that wolves and bears kill some, Schrage said. Brainworm and
winter ticks also have killed some calves.
The radio collar study showed that warming temperatures likely
were a problem, but the next stage of research is geared to look at
the sorts of habitat moose use when temperatures rise.
Researchers in a couple areas of the northeast are deploying
satellite collars, which offer more precision than radio collars,
to get a handle on habitat use.