October 18, 2019
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Ticks kill 50 percent of moose calves in Maine, but that’s not the case in the rest of North America

John Holyoke | BDN
John Holyoke | BDN
The 53rd North American Moose Conference was held this week at Sugarloaf in Carrabassett Valley.

CARRABASSETT VALLEY, Maine — For more than a decade, Mainers have learned more than they ever thought they would have to learn about a small creepy-crawly that has had a tremendous impact on moose — especially young moose trying to make it through their first winter.

Research by the Maine Department of Inland Fisheries and Wildlife has confirmed that winter ticks are moose killers, and in some years, more than 50 percent of moose calves in the research study have succumbed after serving as hosts to thousands of ticks.

At the North American Moose Conference, a gathering of moose researchers that was held at the Sugarloaf resort this week, biologists from other states and provinces shared their own views on ticks, global climate change that has helped ticks thrive and other threats to the moose herds that they manage.

And while winter ticks aren’t a universal threat, moose are facing a variety of other threats in different ecosystems.

Glenn DelGuidice of Minnesota, who serves as the moose and deer project leader for that state’s Forest Wildlife Unit, said that unlike Maine, where calves seem to fare pretty well until later in the winter when the effect of the ticks builds up, Minnesota loses its calves earlier.

“We had a very high neo-nate mortality. And two-thirds of that was wolf predation,” DelGuidice said.

DelGuidice said other parasites such as brainworm and liver flukes are more of a threat to moose in Minnesota than winter ticks typically are, and the spread of brainworm is helped along by the state’s burgeoning deer herd. But the four-legged predators are taking their share of moose, too.

“[We have] 2,600 to 3,000 wolves,” he said. “The moose calves — the newborns — are vulnerable for the first 30 to 50 days.”

Quebec has a thriving moose herd that exists in two parts — one north of the St. Lawrence and one to the south. Maxime Lavoie, a moose biologist for the province, said climate change may actually expand the range for those moose north of the St. Lawrence, which would be able to migrate even farther north should habitat change. That section of Quebec does have a wolf population, he said.

And in the south, where conditions are similar to those across the border in Maine, Lavoie is preparing to do some research similar to that which has been done across the border.

“With the climate change, maybe we’re going to see an increasing impact of the winter tick, so we’re going to make a study about that to better look into those interactions,” he said.

New Hampshire, as you might expect, has similar winter tick concerns to Maine. And the situation is getting worse each year, according to moose project leader Kristine Rines of the New Hampshire Fish and Game Department.

“When we did our first study we realized that winter tick was the driver [to a population decline], and it has only become significantly worse over the intervening 10 years,” Rines said.

A decade ago, the state had experienced just a single die-off of more than 50 percent of research calves — called an epizootic — over the previous five years. Now, they’ve had a similar die-off four times in the past five years.

The overwhelming cause: winter ticks.

According to a longtime researcher from the Canadian province of Manitoba, curtailing the hunting of a diminishing herd is key.

“Our moose population right now, based on estimates from this past winter, is only 12,000 moose,” Vince Crichton said. “And we were up between 30,000 and 40,000 about 15 years ago. The big issue is the unregulated harvest by our aboriginal people.”

Crichton said subsistence hunting cannot be limited by the province. He said he is working with First Nation representatives to come up with reasonable solutions.

“We’ve got nine or 10 hunting areas that have an average of 130 moose, and [wildlife officials] still have hunting seasons there,” Crichton said. “What planet are they on?”

And up in Alaska, Terry Bowyer, an emeritus senior scientist with the University of Alaska’s Institute of Arctic Biology, said winter ticks are not even on the radar.

“Winter ticks aren’t a problem there. They don’t exist,” Bowyer said. “The main problems facing moose in Alaska are predators. A combination of wolf and bear predation can on occasion hold moose at very low densities.”



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