REGIONAL— DNR wildlife officials announced this week that the northeastern Minnesota moose population appears to be stable, and that’s a positive development after noted declines ten years ago …
REGIONAL— DNR wildlife officials announced this week that the northeastern Minnesota moose population appears to be stable, and that’s a positive development after noted declines ten years ago suggested the population might be crashing.
State biologists pegged the latest population estimate at 4,180 moose, a sizable increase over the estimate of 3,030 last year. Wildlife officials noted that the two estimates remain within the margin of error, but this year’s results do suggest that there may well be more moose out on the landscape than last year. The estimates are developed each year based on an aerial survey conducted in mid-January.
According to the latest moose data, the DNR believes (with 90-percent confidence) that the moose population in the region is somewhere between 3,250 and 5,580. That compares favorably to last year’s estimated population range of between 2,320 and 4,140.
Tower area DNR wildlife manager Tom Rusch said the numbers may be less important than the trend. “You like to see the point estimate going in an upward direction, but I think the bigger picture here is it’s encouraging to see eight years with a stable moose population.”
The past several moose survey results suggest that fears of a crashing moose population may have been premature. While the future of the species in Minnesota remains in question given the warming climate, it appears that the moose is holding its own in the region, albeit at lower numbers than 15 years ago, when the region’s moose population peaked at just over 8,800 animals. “In the short to medium term, we’re likely to keep seeing moose in the forests, lakes and swamps of northeastern Minnesota,” said Glenn DelGiudice, DNR moose and deer project leader. “But their long-term survival here in Minnesota remains uncertain.”
The moose population appeared in good shape in the region up until 2010, when the survey suggested a population dip from 7,840 animals in 2009, to 5,700 one year later. That downward trend appeared to accelerate until 2013, when an estimate of 2,760 prompted the DNR to suspend the moose season and undertake more intensive research on the species in hopes of learning the causes of the decline.
It now appears that the 2013 estimate may have been an outlier, since estimates rebounded into the low-4,000 range the following year. And numbers since have held remarkably steady ever since. The 2018 estimate was the lowest since the 2013 survey, but this year’s robust rebound suggests last year’s estimate was probably on the low side.
Plentiful moose in
The latest survey results continue to show robust moose numbers in areas with good habitat and low deer densities. And it’s increasingly clear, both from research and anecdotal observations, that forest fire is key to moose success. Rusch said that was apparent during one day of this year’s aerial survey when researchers flew over some of region’s largest recent burns, including Pagami Creek, Kekakabic, and Ham Lake. “In one day, on just eight plots, we counted 185 moose. That’s phenomenal,” said Rusch. “Those big fires have had population level ramifications.”
Rusch said survey results over large clearcuts have shown less dramatic results, even when they are designed to mimic the disturbance caused by fire. “We can’t fly big cuts and find this number of moose,” he said.
Big burns take about three years to recover, but once regrowth becomes available above the snow, the survey results show that moose take advantage in big numbers.
“It makes you all fired up to see that,” said Rusch, who notes that it demonstrates that in the right habitat moose can still do very well in Minnesota, at least for now.
Exactly why moose benefit so much from fire hasn’t been proven, but biologists think the answer is pretty straightforward. Rusch said fires undoubtedly clear the land of parasites like winter ticks, which can be a major burden for moose. Over time, tick numbers can build up, but a hot fire can virtually wipe them out across a large area, probably for years.
Fire also kills off land snails, which facilitate the transfer of parasitic brainworms from deer to moose, according to Mike Schrage, a Fond du Lac band biologist who has documented the affinity of moose for fire. The land snail is what’s known as an intermediate host, notes Schrage, who spoke to the Timberjay about his research last year.
The snails ingest the brainworms, most likely from deer scat, and then spread the disease when moose accidentally consume the snails while browsing vegetation. Each time a fire rolls through, it clears the landscape of the snails that make the spread of the deadly brainworm possible and it can take many years for the brainworm transmission to begin again.
Finally, fire tends to release a lot of nutrients into the soil, and that means regenerating growth is likely highly nutritious for moose, which improves their ability to fight off disease, or fend off predators like wolves. “We’re talking about an 800 to 1,000-pound animal that makes its living on leaves and twigs,” said Schrage. The quality of that forage makes a huge difference.
Causes of the decline
After several years of intensive research of GPS-collared moose in the region, DNR biologists have concluded that there’s no one factor behind the population decline. Instead, it’s a combination of factors, including relatively high predation from the state’s robust wolf population along with a host of diseases caused mostly by parasites, such as brainworm, winter ticks, and liver flukes.
Whitetail deer are known to be carriers of both brainworm and live flukes and moose success appears increasingly to be linked to lower whitetail density.
According to DelGuidice, moose reproductive success and adult survival have the greatest impact on the annual count and dynamics of the moose population over time.
“We know from our research that adult female moose are getting pregnant,” DelGiudice said. “The problem is there aren’t enough female moose that are successfully producing calves and raising them to one year. That’s a significant challenge in our efforts to maintain Minnesota’s moose population.”
The DNR’s detailed field research has shown that wolf predation has consistently accounted for about two-thirds of the calf mortality and one-third of the adult mortality. In some cases, injuries suffered during predation attempts – not the predation itself – ultimately killed the adult moose. In others, sickness or disease likely made the adult moose more vulnerable to predation, according to researchers.