October 16, 2013 - CHOTEAU, Mont. Across North America in places as far-flung as Montana and British Columbia, New Hampshire
and Minnesota moose
populations are in steep decline. And no one is sure why.
Twenty years ago, Minnesota
had two geographically separate moose populations. One of them has virtually disappeared since the 1990s, declining to fewer than 100 from 4,000.
The other population, in northeastern Minnesota, is dropping 25 percent a year and is now fewer than 3,000, down from 8,000. (The moose mortality rate used to be 8 percent to 12 percent a year.) As a result, wildlife officials have suspended all moose hunting.
Here in Montana, moose hunting permits fell to 362 last year, from 769 in 1995.
“Something’s changed,” said Nicholas DeCesare, a biologist with the Montana Department of Fish, Wildlife and Parks
who is counting moose in this part of the state — one of numerous efforts across the continent to measure and explain the decline. “There’s fewer moose out there, and hunters are working harder to find them.”
What exactly has changed remains a mystery. Several factors are clearly at work. But a common thread in most hypotheses is climate change.
Winters have grown substantially shorter across much of the moose’s range. In New Hampshire, a longer fall with less snow has greatly increased the number of winter ticks, a devastating parasite. “You can get 100,000 ticks on a moose,” said Kristine Rines, a biologist with the state’s Fish and Game Department.
In Minnesota, the leading culprits are brain worms and liver flukes. Both spend part of their life cycles in snails, which thrive in moist environments.
Another theory is heat stress. Moose
are made for cold weather, and when the temperature rises above 23 degrees Fahrenheit
in winter, as has happened more often in recent years, they expend extra energy to stay cool. That can lead to exhaustion and death.
In the Cariboo Mountains of British Columbia, a recent study pinned the decline of moose on the widespread killing of forest by an epidemic of pine bark beetles, which seem to thrive in warmer weather. The loss of trees left the moose exposed to human and animal predators.
In Smithers, British Columbia, in April, a moose — starving and severely infested with ticks — wandered into the flower section of a Safeway market. It was euthanized. Moose
dies after B.C. Safeway stroll.
Unregulated hunting may also play a role in moose mortality. So may wolves in Minnesota
and the West.
Scientists and officials say other factors could still emerge.