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A Wilder View: Wolves impacting deer and moose behaviors in important way

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Posted at 11:45 AM, May 26, 2022
and last updated 2022-05-26 15:16:06-04

MISSOULA - This edition of A Wilder View takes a look at how the mere presence of wolves can shift the behaviors of deer and moose keeping a parasite called brain worm at bay.

Moose are the largest of all the deer species weighing in at more than 1,500 pounds and standing taller than six feet high. They are an astonishing species to see in the wild but their populations are declining in certain areas.

One reason is because of a tiny parasite no bigger than a single strand of hair called brain worm, a common parasite found in whitetail deer. Deer and moose can pick up this parasite by accidentally ingesting snails while eating food

For deer, things are seemingly relaxed as the parasites live in the spine and the brain near the skull. Adult worms actually live in the tissues that encase the brains of the deer. But for moose, the parasites are a different story.

“What happens is those larvae don’t have the same road map and end up tunneling through the spinal cord and brain of moose and that causes damage and disease,” explained University of Minnesota Assistant Professor Tiffany Wolf.

Because of these effects, this tiny parasite is causing a steep decline in moose populations.

"We began researching moose population decline over a decade ago and discovered that brain worm is the primary driver of adult mortality,” said Grand Portage Band of Lake Superior Chippewa Director of Biology and Environment Seth Moore.

About 25% of moose die from this parasite. A lot of fieldwork had to be done to find this out.

“We capture moose by helicopter, Moore explained. “Scout the area by air. The helicopter will try and get that moose into an open area [and] put a dart in it.

They anesthetize moose with a safe drug from the dart.

“The drug combination that we use for moose are very well established in the literature,” Moore said. “We work hard to maintain animal welfare and human safety and often in that order because it’s risky work for both.”

“Once the animal is on the ground, we’ll put the collar on, we’ll collect samples and then we’ll release the animal,” Moore continued.

Not only did all of this work find that moose are immensely impacted by brain worms but it provided further evidence of the vital role predators play in ecosystems.

“Predators are important from a disease perspective that we don’t always think of right off the bat,” Wolf said. “We know that predators can impact disease transmission among their prey primarily by killing them — removing the sick and the weak.”

That’s the direct benefit predators — and specifically in this study’s case wolves — can have in keeping an ecosystem healthy. “If deer and moose are overlapping there's a greater risk of transmission of this disease,” Wolf noted.

But the mere presence of wolves can shift the behaviors of deer and moose keeping these parasites at bay. “They utilize different habitats based on predator risk,” Wolf said. “Less overlap between the two species which ultimately means less disease risk for moose from deer.”

Essentially deer and moose choose habitats based on different needs and one of those needs is refuge from predators. “That behavioral response with the mere presence of predators can impact these species overlap,” said Wolf.

It's important to note how much research must be done to prove something substantial. “I think really doing some follow-up work on this is absolutely critical,” Moore said.

This enables them to continue the line of research to get better and more defined answers.

The research leveraged data gained from a long-term ecosystem health research program led by the Grand Portage Band of Lake Superior Chippewa and the University of Minnesota. Moore outlined the importance of diversity, equity, and inclusion in the biological realm.

“We come to the table as equal peers conducting this research and leading this research where I think in the past tribes were often times more passive participants or were the object of study rather than the drivers of study.”