U OF M PROFESSOR TIFFANY WOLF HAS TROMPED THROUGH SNOW, PULLED TICKS, STUDIED BLOOD SAMPLES, AND EVEN STARTED A CROWDFUNDING CAMPAIGN IN HER EFFORTS TO FIND OUT WHAT’S KILLING MINNESOTA’S MOOSE. CAN SHE FIGURE OUT HOW TO STOP THEIR DEMISE?
Last fall, Tony Swader loaded up his rifle and hiked into the woods in search of a moose. Swader is 64 years old and a member of the Grand Portage Band of Lake Superior Chippewa, whose reservation lies near the tip of Minnesota’s Arrowhead region.
The band counts moose among the wildlife that have helped them survive for centuries. Each year, during rutting season, a hunting party kills an animal or two. They preserve or eat the meat, and boil and scrape the hides to make them into drums. The bones become whistles and tools.
Swader has been hunting moose since he was a teenager, but in recent years, he’s noticed a sharp decline in the species’ population. Official numbers support his observations: Aerial surveys conducted by the Minnesota Department of Natural Resources (DNR) showed a 50 percent plunge in the moose population—to fewer than 4,000 animals—between 2006 and 2012, when the state enacted a moratorium on hunting the iconic creature. Recent figures suggest the state population has stabilized, hovering between 3,250 and 5,580 animals.
The DNR’s own efforts to investigate the decline have been slowed by a statewide ban on collaring moose. Governor Mark Dayton ended the practice in 2015 after dozens of calves ﬁtted with radio collars turned up dead, possibly abandoned by mothers who were spooked by the strange-looking devices. The decision effectively gutted the DNR’s $1.6 million plan to track every moose in Minnesota, and opponents say the ban robs researchers of an essential data-gathering tool. Collaring adult moose, they note, is rarely problematic.
But not all studies ended. The University of Minnesota’s Tiffany Wolf has been working with the Grand Portage band to better understand the causes of moose mortality—and find ways to reverse the species’ decline—for more than a decade. Under rights granted in an 1854 treaty, the Chippewa are exempt from the state’s hunting ban and continue to harvest moose. However, the band is also committed to the animal’s long-term survival, says Seth Moore, the band’s director of biology and environment.
“A healthy moose population is a hallmark of a healthy, northern boreal ecosystem,” says Moore, who earned his doctorate in water resources science at the University of Minnesota in 2008. “A decline in the moose population indicates something is amiss with our ecosystem.”
Moore and Wolf, an assistant professor in the College of Veterinary Medicine, have collared and tracked roughly a third of the 60 moose that roam the Grand Portage reservation. (The collaring ban doesn’t apply to tribal lands.) And a newly formed collaboration allows them to do research in nearby Isle Royale National Park, where the moose population is thriving.
Wolf, who grew up in Louisiana, says she recognizes how strongly Minnesotans identify with the moose. Many are distressed to learn the population is dwindling. “Moose are culturally important to most Minnesotans,” she says. “It’s a species that a big part of our population doesn’t want to lose.”
WHY MOOSE ARE DYING
Moose began vanishing from Minnesota in the 1990s, in large part because of human impact on the region’s ecosystem. Landscape changes have dramatically altered moose habitat in recent years—though not necessarily in the ways you might imagine.
Solitary creatures, they prefer to sleep in the shadow and shelter of old-growth forest. But when it comes to diet, moose—the name, in Algonquin, means “eater of twigs”—like to snack on soft woody plants found in areas of fresh growth. They browse leaves, roots, tall grasses, pine cones, and the occasional aquatic plant. Areas recently swept by wildfire or opened up by logging are particularly attractive, as plants regrow and emit tender new shoots. Ironically, as Minnesota’s logging industry declined and its forested areas began to thrive, the moose population thinned.
Climate change has also affected the species, whose thick coats are increasingly burdensome as summers get longer and hotter. Warmer Novembers and Decembers lengthen tick season, extending the window when the pests typically attach themselves to their hosts in preparation for winter. Some animals become anemic as the ticks suck blood from their veins, Moore says. Others try to ease the itching by scraping their skin against a tree, removing large clumps of hair, which can lead to death from hypothermia.
Predators have shaped the moose population as well. Black bear regularly kill and eat young moose, and a lone wolf can easily bring down an injured or ailing adult. A pack of wolves is capable of felling even the largest bull, and estimates show wolves account for upward of 60 percent of calf deaths in Minnesota. As the state’s wolf population increased—from an estimated 400 statewide in the 1950s to more than 2,660 today—moose numbers have taken a hit.
But the biggest threat to moose may come from white-tailed deer—or rather, Parelaphostrongylus tenuis, a parasite that reproduces in the lining of the animal’s brain. Deer are seemingly unaffected by P. tenuis, but moose suffer terrible consequences as the parasite tunnels through neurological tissue. As white-tailed deer have spread into northern Minnesota, inhabiting once-dense forests now punctured by roads and developments, they have begun to overlap with moose. As a result, P. tenuis larvae—after being passed in deer feces, attaching to slugs and snails, and then being ingested by foraging animals—has begun to decimate the moose population.
The simplest way to reduce brainworm in moose, one might conclude, is to kill more deer. But as Wolf notes, “That’s a really complicated approach because most people don’t want to see white-tailed deer populations reduced to a low-enough density that transmission won’t occur.” The same goes for reducing black bear numbers and wolf populations. So how do we find a way to keep threats to moose in check?
HUNTING FOR CLUES
Capturing and collaring a moose takes a team of people. At Grand Portage, the operation usually happens in January or February, and begins with a spotter plane calling in the coordinates of a freshly located moose. A helicopter flies to the spot and herds the beast like a border collie does sheep, moving the animal into position so a darter can land a tranquilizer shot in its back, hip, or shoulder. Once the moose drops to its knees, the darter begins collecting samples of blood, hair, urine, and feces.
Wolf and Moore arrive soon afterward. They assess tick loads and examine body condition. They attach or adjust a radio collar, as needed. Wolf checks to see if cows are pregnant, and if they are, she implants a vaginal transmitter that sends a signal when the calf arrives in the spring. “It’s our opportunity to see what our animals are looking like,” Wolf says of the capture. Before departing, she injects a drug that reverses the sedative. Within five minutes, the moose is back on its feet, trotting away.
Moore tracks moose mortality causes carefully, and the results have proven insightful: Predators kill a handful of the Grand Portage herd every year; a car crash occasionally claims a creature; tick infestations account for roughly one in five moose deaths. The biggest cause by far, though, is brainworm, which accounts for 35 percent of adult mortality.
“That should give us a hint about what we need to be managing,” he says. “We need to do something about brainworm because it’s a major factor.”
Wolf, who holds a doctorate in wildlife epidemiology and ecosystem health from the University of Minnesota, wants to do just that. Her research into P. tenuis is three-pronged. First, she’s trying to map the overlap of white-tailed deer, moose, and brainworm infections in order to pinpoint locations where changes in wildlife management practices can have a big impact on transmission of the parasite. Second, she’s sampling moose feces in hope of identifying the particular gastropods that serve as temporary hosts in the transfer of brainworm from deer to moose. Finally, she’s examining the genetics of the parasite in deer pellets, looking for differences in P. tenuis DNA that might shed light on ways to block transmission.
Wolf and Moore have sought public grants to fund their work and benefitted from a gift from the Van Sloun Foundation. A few years ago, Wolf set up a U of M crowdfunding site so members of the public could support aspects of the team’s work. Nearly 150 people have contributed more than $10,000 to the campaign. “Those dollars have allowed us to do some pilot research that’s often hard to get funded because it hasn’t been fully established yet,” Moore says.
CAPTURING, COLLARING, COLLABORATING
What does a healthy moose population look like? That’s hard to say in a world irrevocably altered by human impact. But Wolf and Moore believe the answer may be found on Isle Royale. A national park since 1940, the island in the middle of Lake Superior was, until recently, home to an estimated 2,060 moose, just two wolves, and not a single deer. (An attempt to introduce whitetails in 1906 failed.)
Essentially unchecked by predators, the moose were beginning to overbrowse certain plant species before the federal government decided to rebuild the park’s wolf population. They also had no exposure to brainworm.
The Grand Portage Chippewa initially objected to the wolf translocation plan, arguing that their ancestral ownership of the island gave them the right to harvest the moose and bring down the herd population. But as the feds and other collaborators doubled down on the plan, Moore saw benefits in reversing course: In exchange for access to data, he and Wolf would share their expertise in collaring. “They wanted to see the impact of wolves on the moose population,” Moore says, “so we brought over four wolves with collars and offered to assist with a moose-collaring program.”
Wolf says her moose research will benefit significantly from the three-year Isle Royale collaboration, which brings together researchers from Isle Royale National Park, Michigan Tech University, and the State University of New York. “To have partners that are interested in working together and sharing data collaboratively is such a huge opportunity,” she says. “You don’t often get the opportunity to look at data across populations like this, so it’s pretty exciting.”
Meanwhile, back home in Grand Portage, Tony Swader is dreaming of the day when moose are plentiful again. He’s imagining the next hunt and remembering the magnificent beasts that have eluded him over the years. “Moose are surprisingly stealthy in the woods,” he says. “It’s hard to believe an animal that size can disappear right in front of you in a heartbeat.”
Joel Hoekstra is a Minneapolis writer and editor.
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