Moose populations in Minnesota crashing as climate change deteroriates health

By Daniel Cusick / Scientific American

If moose disappear from the boreal forest of northern Minnesota, as some biologists predict, they will not exit with a thunderous crash. Climate extinctions come quietly, even when they involve 1,000-pound herbivores.

Experts who have studied the Northwestern moose — Alces alces andersoni — believe they are witnessing one of the most precipitous nonhunting declines of a major species in the modern era, yet few outside Minnesota fully appreciate the loss.

The moose is an iconic species whose existence is woven into the social, economic and cultural fabric of this region. Its elongated head and wide antlers are emblazoned on everything from T-shirts to tire flaps. The 1960s cartoon character Bullwinkle J. Moose and his flying squirrel friend Rocky were residents of the fictionalized town of Frostbite Falls, Minn.

But the animals that inspired Bullwinkle are not what they were. Here, even healthy bulls — whose size, strength and rutting prowess make them the undisputed kings of the North Woods — are dying from what appear to be a combination of exhaustion, exposure, wasting disease triggered by parasites and other maladies.

The biologists are baffled and also helpless.

Mark Lenarz, who retired in March from the Minnesota Department of Natural Resources (DNR), where he led moose research efforts, said it’s not like the TV show “CSI: Crime Scene Investigation.”

“Unlike ‘CSI,’ it’s very hard to identify in the field exactly what an animal is dying from,” he said. “We know something about the symptoms” of distressed moose, he added, “but we don’t necessarily know the exact causes of mortality.”

What Lenarz and other experts do know is that a variety of climate stressors — including higher average annual temperatures, a long string of very mild winters, and increasingly favorable conditions for ticks, parasites and other invasive species — are conspiring to make northern Minnesota a moose graveyard.

Since 2002, Minnesota DNR specialists have put radio collars on 150 healthy adult moose; 119 subsequently died, most of them from unknown causes, according to wildlife officials. Car and train collisions accounted for 12 mortalities, while wolves were culpable in just 11 deaths.

Sudden collapse of herds
Meanwhile, annual surveys taken from helicopter overflights show that the state’s primary moose population, in the state’s northeastern Arrowhead region, has been halved in just six years, dropping from 8,840 animals in 2006 to just 4,230 this year. The decline mirrors a similar collapse a decade ago in the state’s northwest corner, where moose plummeted from an estimated 4,000 animals in the mid-1980s to less than 100 by the mid-2000s.

While some monitoring of moose had occurred in the 1990s, most of the animals were gone before scientists could examine cause-and-effect relationships. In the Arrowhead, however, experts are watching mass mortality, discovering multiple moose carcasses in the same area, including animals that appeared relatively healthy only a few years before.

It’s not just the occasional sickly moose succumbing to common causes of mortality, said Lenarz. “We’re out in the

field collecting dead radio-collared moose, and we were finding other moose that had died along with them.”

Similar mysterious deaths of one or more moose have been documented in Voyageurs National Park, where the National Park Service had launched its own radio-collar study of the animals, and in the Boundary Waters Canoe Area Wilderness, where moose sightings used to be routine for visitors but are increasingly rare.

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3 thoughts on “Moose populations in Minnesota crashing as climate change deteroriates health”

  1. Has the DNR considered the effects of pesticide residue runoff into the lakes and sloughs where the moose feed? Pesticides are affecting the frog populations and they can probably have a toxic effect on the moose, also.

  2. I do not deny that we are going through a period of warming nor that it may in fact be having an impact on the moose, but I am interested in what actual evidence they have that this decline is caused by warming.

    They say the northwest population pretty much completely crashed a decade earlier. Do they have climate data suggesting the northwest warmed before the northeast?

    My fear is that the cause is something other than warming but warming is being blamed as a convenient excuse rather than out of scientific data.

    Deer population are on the rise, and there is a brain worm deer carry that has a very bad effect on Moose. Could the real problem be too few top predators (wolves and cougars) to keep the deer populations in check? What about other diseases that may have a reservoir species allowing it to defy the principle of population immunity?

    When the Golden Toad population crashed, warming was blamed there too. We didn’t know about the impact of chytrid on amphibians at that time, and now the Golden Toad crash is eerily like other frog population crashes we know are from Chytrid.

    We need to be very careful when making a scapegoat out of climate change. The data needs to be solid and there needs to be a way to falsify the hypothesis. Otherwise the real reason may not be discovered and corrected, resulting in continued plummet until population extinction, and confirmation bias will continue to blame Global Warming.

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