Monday, February 6th, 2023
Monday, February 6th, 2023

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New count doubles NE moose estimate

Field Editor

Tower, Minn. Northeastern Minnesota’s moose population hasn’t
changed, but the DNR’s 2004 estimate of their numbers more than
doubled from previous counts because biologists are using a new,
and more effective, survey technique. The population is estimated
at 8,500 to 11,000 based on the 2004 survey. Previous estimates
since 1997 were around 4,000 moose.

“This does not mean we have more moose,” says Tom Rusch, DNR
area wildlife manager in Tower.

The increased population estimate is due to two changes made in
the annual winter moose count. First, biologists began using a
helicopter rather than fixed-wing aircraft to fly the survey.
Second, they used a new method to estimate the number of moose they
don’t see when flying a survey plot.

The annual survey has long been troublesome for state and tribal
wildlife biologists who share moose management duties in the
Arrowhead region. Moose are most visible in early winter, when
their black forms contrast with a snowy background. However, late
arrival of snow cover or inclement weather often delayed the survey
until midwinter, when moose retreat to conifer cover for shelter
from the cold. As a result, it was difficult to fly the survey at a
consistent time period and, in some years, was challenging to
observe moose from the air. Since 1997, the survey has started Jan.
1, which assures adequate snow cover and provides more consistency
to the count.

Mark Lenarz, DNR wildlife research biologist in Grand Rapids,
says the new survey technique will help biologists overcome past
problems. Using a computer modeling process development for a
winter elk survey in Idaho, biologists can estimate the number of
moose they are not observing in heavy cover.

Lenarz says that when helicopter observers see a moose, they
rank the amount of visual obstruction. For instance, the ranking is
zero for a moose standing in an open clear cut, but may be 70
percent for an animal standing in conifer cover. Data of moose
observed and the amount of visual obstruction is entered into a
computer program that arrives at a population estimate.

To test the accuracy of the new method, biologists flew test
plots known to contain radio-collared moose from an ongoing
research project. They counted moose and measured visual
obstruction. If the collared moose wasn’t sighted, they located the
animal with radio telemetry. The collared moose were seen about 50
percent of the time. The moose in the test plots were more visible
on warm days and disappeared into the conifers when it was cold or
windy.

“I had a gut feeling that was how it would turn out,” Lenarz
says.

Using a helicopter makes it much easier to see moose from the
air. Rusch, who has participated in the survey for a number of
years, says that a fixed-wing plane travelled at 80 knots or more,
giving an observer four or five seconds to spot moose down below.
The helicopter goes much slower, about 60 knots, allowing more time
for observation.

“Too often in the past you’d see good habitat or moose tracks,
but you were going too fast to see the moose,” Rusch says. “Going
more slowly with a helicopter gives you more time to look for them.
We absolutely saw more moose this year.”

The higher population estimate won’t affect the number of
permits available for annual state and tribal hunts at least until
more population data is available. Lenarz says the new survey
represents a starting point for population data. The higher
estimate can’t be interpreted as a population increase, nor can it
be compared to previous estimates.

Moose densities in northeastern Minnesota range from about one
to three animals per square mile. By comparison, the moose
population on Isle Royale once reached nine per square mile just
prior to a population crash. Biologists are uncertain why the
Arrowhead herd doesn’t increase in numbers or expand its range. To
learn more about the herd, two years ago the radio-telemetry study
was begun.

So far, the study indicates Minnesota moose have a high
mortality rate, though biologists are unsure why and how it affects
the overall population.

Lenarz says researchers try to collect samples from dead moose,
though it is difficult do to so if the animal is frozen or has been
scavenged by wolves. He said one moose appeared to be intact, but
closer examination showed a weasel or pine marten had entered the
body cavity through the rectum and scavenged most of the internal
organs.

Rusch says that both moose and white-tailed deer are taking
advantage of new habitat created in the Boundary Waters Canoe Area
Wilderness by the 1999 blowdown. In some places, the Forest Service
has removed blowdown with prescribed burns, while in others the
animals are living in places where partial blowdown created young
forest.

While the new survey technique is hoped to improve the accuracy
of the northeast moose count, Lenarz doesn’t think it can be
effectively used to count moose in northwestern Minnesota, which
has suffered a substantial population decline. In the northwest,
the moose are too scattered to be counted using this method.

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