The hunts have been canceled, and the studies are ongoing. Yet moose are still dying, and scientists are stymied.
Stress and brain worm, both exacerbated by a changing climate, may be playing off each other in moose deaths, which are twice the normal rate for sustaining the animal’s population, The New York Times reported on March 5. The bottom line, though, is that it's still a mystery.
Winters are both warming and growing shorter—this year’s seemingly interminable frigid temperatures notwithstanding—and this may both compromise the moose’s immune system and boost the number of white-tailed deer, which carry brain worm, a parasite that is fatal to moose.
Native experts and scientists have been studying the die-off, which The New York Times also reported on in October. Several tribes canceled their seasonal hunts while the decline was studied.
“I’m not necessarily convinced that brain worm is the silver bullet that’s killing all of the moose,” said Seth Moore, a wildlife biologist in Grand Portage, to The New York Times. “There are a number of different issues.”
Minnesota seems to be the epicenter of the die-off, as New Scientist reported back in October, but it is occurring all along the southern edge of the moose’s range, including places like Sweden. And the causes are disparate, leading researchers to suspect an underlying cause that all have in common.
"The fact that you've got different proximate causes killing off the moose suggests there's an underlying ultimate cause," said Dennis Murray, a biology professor at Trent University in Peterborough, Ontario, Canada, to New Scientist.
“The combined effects of climate change, parasitism and poor nutrition are involved in the die-off, and in the foreseeable future these factors likely will drive the population to extinction,” Murray wrote on the web page describing the lab’s research. “Consequently, we predict that over the next decades a widespread northward push of the distributional limit for moose will occur.”
The New York Times has a stirring video posted on its site with the story. Minnesota Mystery: What’s Killing the Moose? also quotes Tony Swader, Grand Portage Band of Chippewa.