Moose population decline in Minnesota

[Lee Borgersen]

2/11/2011

 
Moen speaks in Ely: Moose population decline in Minnesota is still a mystery

by Joe Domich

Tuesday night, local residents were treated to a lecture/slide show on "Moose in Minnesota", at the theater in the International Wolf Center.

Ron Moen, a University of Minnesota-Duluth professor is involved in a project to study moose, not only in Minnesota but in the Quetico wilderness area of Ontario as well.

Moen spoke for over an hour on some of the findings of the study, thus far.

The study seeks to determine, among other things, whether the moose population is in critical decline, the causes of premature death, the foraging patterns of moose, the effects of temperature on moose mortality, the effects of increasing numbers of parasite-bearing white-tailed deer in traditional moose habitat, and moose calving habitats and patterns.

The original phase of the study involved darting or netting moose to install VHF radio collars so that their activities could be tracked by aerial observation. This phase was conducted from 2002 to 2010.

Unfortunately, the use of VHF collars requires flyovers of likely moose populations in order to pick up the radio signals. This method was both expensive and spotty, in terms of results.

For example if a moose died it might be a week to ten days before this fact was recognized, and by that time, the remains were likely to yield no useful information.

The next phase of the study, begun in 2010, involves using GPS, satellite-linked collars which do not require flyovers.

This phase has just begun but so far the results are promising. Information about the moose's activities and locations is provided every 20 minutes, and air temperature data is collected and provided at one-minute intervals.

The collaring activities began in Quetico and stretched south to the Gunflint area and Voyageur National Park, finally ending in the Isabella area of northeastern Minnesota.

According to Moen, in the 1880's the moose range encompassed all of northern Minnesota and stretched much further south than it does today.

As settlement of northern Minnesota increased, the population of moose moved further and further north and concentrated in the northeast and northwest, leaving the north-central area with relatively few moose.

In the 1990s the northwest population of moose virtually disappeared. The area went from over 4,000 animals to almost none.

Climate change, chronic malnutrition, and disease were the primary causes of the decline. Liver fluke infections apparently constituted the greatest single source of mortality.

It is estimated that there are about 6,000 to 8,000 moose in the northeastern range.

Up until about the year 2000 it was estimated that there were only about 4,000 moose in this range.

Technological advances have enabled a revision of that estimate upwards to nearly 8,000 animals, but it is still difficult to obtain an accurate count.

The population is apparently trending downwards based upon data from collared animals. High mortality rates, low reproduction, declining hunter success rates and anecdotal comments from residents in the moose range all suggest that the northeastern moose population is declining.

Moen related some preliminary observations based upon the data collected by the project, so far:

• There are a number of late spring and early summer deaths of apparently healthy adult moose, the reason for which is as yet unknown. This phenomenon is called "tipping disease" or "tipping syndrome", as the animals simply tip over and die.

• The fall survival rate is higher when it follows a cool spring. Warm springs are linked to higher fall mortality rates. The reasons for this are unknown.

• The females' foraging range is about 11 miles; the males' range, about 16.

• Calf-to-cow ratios have been observed at about 80 to 90 calves per 100 cows, which is sufficient to sustain the population, but in the fall of 2010 the observed ratio was only 40 per 100.

• Calf predation is primarily by wolves and mountain lions, but bears can take some calves up to about four weeks of age. Beyond that age, the moose calf can outrun a bear.

• Moose mortality appears to be directly related to temperatures. Moose are able to survive under very cold conditions but can be heat-stressed in winter at temperatures above 32 degrees Fahrenheit. They can be heat-stressed in summer at temperatures of only 60 - 70 degrees F. Is it becoming too hot for moose?

Moen said there is a Moose Advisory Committee which has set goals for the project:

• Inform the public.

• Continue monitoring the moose population

• Focus research on habitat, disease, and parasites.

• Measure the role of thermal conditions upon moose mortality.

According to Moen, most public sightings of moose that have been reported have been in the Boundary Waters Canoe Area Wilderness (on or near portages) and in the Superior National Forest (near roads and highways).

The public is encouraged to report moose sightings and a form is available on the project's website.

More detailed information about the project, its methodology and the preliminary results of the research, including charts, graphs, and photos is available at http://www.nrri.umn.edu/moose/, or simply enter "Moose in Minnesota" to Google or other Internet search engines.