May 20, 2018
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Researchers study moose calf survival rates

Photo courtesy of Maine Department of Inland Fisheries and Wildlife
Photo courtesy of Maine Department of Inland Fisheries and Wildlife
Lee Kantar, the state's moose biologist (left) and Matt O'Neal, moose project biologist, collect biological samples from a moose that will be fit with a GPS collar and join others in the Maine Department of Inland Fisheries and Wildlife's five-year moose research project during work in Aroostook County last week.
By John Holyoke, BDN Staff

Early last week, helicopter crews finished up work capturing and radio-collaring moose in two of the state’s Wildlife Management Districts, adding 83 more moose to a pair of study groups in western and northern Maine.

Over time, those moose — along with the others that were previously captured and are already providing valuable data — will help biologists better understand the survival rate among both adult female moose and their newborn calves.

One thing that has become exceedingly clear over the four previous years of gathering data on the state’s western Maine herd around Moosehead Lake: The winter tick is a particular culprit in the lives of young moose, killing more than 50 percent of the study group calves on an annual basis.

Moose, especially young moose, with tick loads in the tens of thousands, can lose enough blood that they become anemic and die.

The study, in conjunction with work being done in New Hampshire and Vermont, has been set up in part to determine whether ticks play similar or different roles at different degrees of latitude. For instance, do ticks kill fewer moose the farther north you go because the ticks themselves struggle to survive in the cold weather?

Maybe. Maybe not.

The argument seems to make perfect sense, agrees Lee Kantar, the head moose biologist for the Maine Department of Inland Fisheries and Wildlife.

“It would be nice if it was all neat and you could say that. To many people, that’s intuitive,” Kantar said. “Clearly, we know historically about winter ticks, that their distribution only goes so far north. Then you get to a point where snow falls earlier and stays longer and there’s a lot of snow, and there just aren’t winter ticks. So we’re still trying to understand the dynamic of those conditions.”

To that end, researchers at the University of New Hampshire have been trying to study factors that influence winter tick survival and learn if those factors can help predict how well young moose will fare in the locations that are being studied.

The answer: A definite “Maybe. Sometimes.”

“One of [UNH professor] Pete Pekins’ graduate students, last year, tried to tie all that together,” Kantar said. “He was looking at moose densities, winter tick abundance, and then the type of weather conditions, environmental conditions, that affect [tick survival].”

Among those factors: Late summer drought, which kills tick eggs, and early snowfall, which kills larval ticks before they attach to a host like a moose.

That graduate student looked at conditions going back to 2016, and tried to predict whether moose calves in various study areas would suffer mortality rates worse than 50 percent during the winter of 2016-2017. After crunching the numbers, he predicted moose calves would fare better than that in all four study areas.

And he was right … almost.

“That worked for our northern study area [in Wildlife Management District 2], New Hampshire’s study area and Vermont’s study area,” Kantar said. “But calf mortality in our western study area was still above 50 percent.”

Just barely — mortality was 58 percent — but it was above the threshold nonetheless.

“The thing that’s the challenge is that there’s no perfect data on how many moose are in any of those areas,” Kantar pointed out. Another gap in the data: It’s impossible to tell how many ticks are there, either.

Sure, ticks are counted on moose harvested during the fall hunting season, as they have been since 2006. But even those baseline counts can provide data that’s not very precise.

“[Those counts] are mostly bull moose, because that’s what we harvest,” Kantar said. “[And] our study is about cows and calves. Rarely do we have the data to look at calves and winter tick loads in the fall. So there’s some nuances there, as well.”

Last week’s moose-wrangling effort in the western Maine district marks the fifth and final such effort during the current five-year study. Up north, the capture-and-collar effort is heading into its third year. The 15 cow moose captured in western Maine this year will still be monitored until their collars wear out — likely another four years.

So the work continues, with some things — the true effect of winter ticks, for instance — becoming more clear, while other answers remain difficult to tease out from the available data.

“Let’s just look at district 8 [in western Maine]. Are we going to have a good year or bad year for calf mortality?” Kantar said.

If this winter isn’t so hard on the calves, that’ll make one out of the last five that’s been that way. If more than 50 percent die again, it’ll mark five bad winters in a row for calves in that district.

“Either way you slice it, the majority of those five years was bad for calves in that district,” he said. “Are the next five years from now going to be like that? I don’t know.”

So in the interim, Kantar and other biologists will continue to gather data and try to fulfill their mission.

“Ultimately, we want to know about survival rates about cows and calves because they’re so crucial to our moose population, and whether we have growth or decline or stability,” Kantar said. “We want to know how that’s going to work, and we want to be able to predict at least the near future so we can satisfy what the public wants. Which is, they want to see moose, they want to hunt moose, and it seems, more importantly, they want to know that our moose are healthy.”

John Holyoke can be reached at jholyoke@bangordailynews.com or 990-8214. Follow him on Twitter: @JohnHolyoke

 


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