North America’s Moose Populations Are Dying Off, and No One Knows Why

For the last two decades, wildlife officials have noted a steady, mysterious decline in moose populations throughout North America. Now, as moose numbers hit a critical low, scientists are scrambling to uncover the culprit.

Moose in Minnesota have taken the hardest hit. As recently as the 1990s, two separate populations collectively boasted 12,000 animals. Sadly, the latest statistics reveal that this number has fallen by almost 75 percent ― and one of the populations has seemingly vanished, declining from 4,000 to roughly 100 in the span of 15 years. Montana, British Columbia, and the Northeast have also reported a similar, albeit less severe, drop in moose populations.

As New York Times correspondent Jim Robbins notes, the moose epidemic goes far beyond the animals themselves. For one, they generate significant revenue; moose-watching tours in New Hampshire alone bring in $115 million on an annual basis, and many states and provinces have been forced to cut the number of moose hunting permits issued each year. Moose also play a vital role in ther local ecosystems, so fewer moose could have major implications on other forest-dwelling species.

So far, the cause behind this massive die-off has eluded wildlife officials ― but many believe invasive parasites are to blame. Scientists in Minnesota have discovered brain worms and liver flukes inside dissected moose corpses. In New Hampshire, biologists are blaming winter ticks. And the findings of a recent study in Canada’s Cariboo Mountains seemingly point to pine bark beetles, voracious insects that gobble up acres of forests every year and rob moose of a major food source.

These parasitic creatures share a troubling common bond: all of them thrive in relatively warm climates. For this reason, many scientists now believe that climate change is indirectly responsible for the moose die-off.

Another popular theory related to global warming is that moose populations nationwide are suffering from heat stress, which occurs when temperatures reach a certain threshold during the winter months. Moose who suffer from heat stress are forced to use up more energy than their huge bodies can handle, and the result is often death by sheer exhaustion.

But as wildlife biologist Mike Schrage told Minnesota Public Radio, simply pointing a finger at climate change is a problematic strategy. “I do think global warming is having an impact on our moose,” he said. “I think it gets complicated between climate change and a dead moose. Because I don’t think I’m ever going to walk up on a moose carcass and be able to say, oh, it died of climate change. I think there’s a lot that happens in between.”

So, what can be done? Well, for starters, wildlife biologists should pay close attention to the Yukon Territory, where moose populations have remained fairly stable. Three separate surveys were conducted last year, and all found that moose populations in the province were actually higher than expected. Wildlife officials currently estimate that 70,000 healthy moose reside in the Yukon.

Temperature may be the key here, as well, since the Yukon has remained relatively frigid as regions to the south have reported higher temperatures in recent years. Additionally, the province imposes strict regulations on moose hunters; female moose are off-limits, and hunters must apply for tags before and after killing a moose so a game warden can verify the dead animal’s sex.  Earlier this year, one party was fined $30,000 and banned from the sport for 10 years after posting photos of their illegal hunting expedition on Facebook.

Kristine Rines, a biologist with the New Hampshire Department of Fish and Game, has posed another potential solution: hunt more moose to curb the number of parasitic infections. A large number of animals would die immediately, but future generations would potentially be spared from wood ticks, liver flukes, and the like.

There are plenty of different theories floating around about how to address the problem, but all of them are accompanied by the same caveat: no one knows for sure what’s causing the moose die-off in the first place. That’s especially bad news for North America’s second largest mammal as another long, presumably-warmer-than-usual winter rears its ugly head.

Unless otherwise stated, images sourced from Thinkstock Images.