The Race to Save the Moose
Minnesota’s moose are dying. Sophisticated technology and an unprecedented research effort aim to find out why.
by Greg Breining
Photographs by Jim Brandenburg
Down a narrow trail through thickets of balsam fir, field biologist Tom Enright (B.S. ’12) carries a pump-action 12-gauge loaded with rubber “buckshot”—just in case a bear is already on the carcass and attacks. As they walk, other researchers stoop to bag samples of wolf scat, packed with moose hair.
The group leaves the trail and eases single-file through downed trees and spongy sphagnum. “There’s the lake,” Enright says, and they follow the sight of blue water until emerging in the open bog surrounding Outlaw Lake in the no-man’s-land between northeast Minnesota’s Boundary Waters Canoe Area Wilderness and Lake Superior.
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They’re looking for a dead moose calf. The crew of researchers is working on a Minnesota Department of Natural Resources (DNR) project aimed at learning why Minnesota’s moose are dying in such great numbers. Glenn DelGiudice (Ph.D. ’88), an adjunct associate professor in the University of Minnesota’s Department of Fisheries, Wildlife, and Conservation Biology, leads the portion of the study that focuses on calves.
His students take turns swinging a VHF receiver antenna to pick up the staccato mortality signal from the calf’s radio collar. The collar had gone into “mort mode” at 4:13 p.m. the day before, meaning the animal hadn’t moved in six hours. On the previous day, the calf and its mother had moved, though not much—they were probably foraging on the lake shore. Then the tracking data changed. The mother appeared to race deep into the woods, then return to the stationary calf, then hurry back and forth again.
“This is where I think trouble happened,” graduate student Bill Severud had said back at the field station. He pointed to lines superimposed on a Bing map on his computer. “She came back to the kill site a second and a third time.” The tracks on the screen appear to tell a tale of panic and sorrow.
It’s late June, the sun strong. The forest seems filled with hot breath. DelGiudice and crew follow the shore toward the far end of the lake, where the collar is still transmitting. Then Enright calls, “We got our kill site!” Wading carefully through the sedges, they find a scapula, a chip of rib, an ear tag, and a pile of ripe digested browse and milk with the remains of the calf’s rumen. “Oh, nice!” DelGiudice says with startling enthusiasm. “Not much left! You can imagine wolves converging on them out here—[the moose] sinking in the muck!”
A call comes from the end of the lake: Enright and volunteer Ben Betterly have found part of the skull and jaw, cleaned of meat. The radio collar lies nearby, where a wolf likely dropped it. DelGiudice walks up to look. “Oh, nice, nice!”
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|Some estimates indicate that Minnesota’s moose population could drop to zero in this decade.
For these scientists, piecing together the final hours of one calf’s life is part of a much larger effort to understand the precipitous decline of Minnesota’s moose population, which, by some estimates, could drop to zero in this decade. Through previous studies, they know the moose are dying at an unsustainable rate. But they don’t know why—or how to stop it.
The current study relies on some of the most sophisticated tracking technology in wildlife biology. It enables researchers to find a moose within a day of its death so that a necropsy—in the field or at the U’s Veterinary Diagnostic Laboratory—can determine exactly why it died. “Nobody’s done that before,” says DelGiudice. “It’s the GPS technology that’s enabling us to do this study.”
Erika Butler (D.V.M. ’06), a DNR wildlife veterinarian and leader of the adult moose mortality portion of the project, says flatly, “We’re going to know more about these moose [than is known about] any ungulate population in the world.”
If the moose survive. If they don’t, says DelGiudice, it will be a “basic and significant loss on several levels.” Biologically, it means a loss of diversity of a key species, which might destabilize northern ecosystems and communities. Recreationally, it is the “loss of a living, breathing part of what most Minnesotans enjoy and value,” he says. “We, the stewards, must take a harder look at the bigger picture and our priorities, our management philosophy and strategies, and wonder what might be next if we don’t make thoughtful and informed changes.”
Moose once shared northern Minnesota with two other large members of the deer family—elk in northwestern Minnesota and woodland caribou in the northeast. Excessive hunting wiped out elk by the early 1900s. (Only later were they reintroduced.) Logging and settlement set off a complex chain reaction that caused caribou to fade northward into Canada. Moose filled the void, multiplying by the late 1900s to some 4,000 animals in northwestern Minnesota and 8,000 in the northeast.
By 2000, the northwestern population was crashing. The last time the DNR flew a census, in 2007, researchers counted 18 moose and pegged the total population at fewer than 100.
In the northeast, moose still numbered 8,800 in 2006. But there were signs of trouble. Researchers coined the term “tip-overs” for moose that, while in the prime of life and with full stomachs, simply collapsed and showed symptoms of extreme malnourishment. “We lost more than a third of our moose population in one year,” says Butler. Today, the northeast population is about 2,700.
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|Glenn DelGiudice and Erika Butler measure the body fat on a tranquilized and radio-collared moose in Lake County in 2011.
Photograph by John Meyers/DULUTH NEWS TRIBUNE
There are many ways a moose can die. Indeed, for such large, powerful animals, they seem almost fragile.
Moose starve at the end of hard winters. They lunge to forage higher and get their heads stuck in the forks of trees. They die on highways and railroad tracks. Rut-addled bulls even spar with locomotives. They break through ice and drown. They fall off cliffs.
Black bears gobble up newborns. Wolves kill larger calves and adults. Humans have also been significant predators. Ojibwa Indians have long hunted moose for food and clothing. Though non-Indians were formerly permitted to hunt moose, the DNR closed the northwestern Minnesota season after 1996 and in the northeast after last year.
Most insidious are parasites and illness. Moose are afflicted by brucellosis, pus pockets, pinkeye, abscesses in the jaw, degenerative joint disease, osteoporosis, toxoplasmosis, parasitic flatworms, liver flukes, various species of tapeworms, tissue worms, lung nematodes, gastrointestinal nematodes, arterial worms, footworms, abdominal worms, and rumen worms.
Of all the pests that afflict moose, three are most likely to kill them. The hydatid tapeworm swims through a moose’s bloodstream to its lungs, where it forms golf ball–sized cysts that reduce stamina and make the moose easy prey for wolves. Winter ticks, each swelling to the size of a peanut, feed a dozen per square inch, up to 100,000 on a single moose. Tick-ridden moose may rub off all their hair. Loss of blood causes anemia, which in turn produces fluid around the heart. The moose die of malnutrition and emaciation. Finally, a meningeal nematode known simply as “brain worm” bores into a moose’s spinal cord, brain, even its eyes. Moose walk in circles—not an effective strategy for escaping wolves—or can wander for hundreds of miles.
Butler suspects some combination of these organisms and their attendant health problems is responsible for the fact that, on average, 25 percent of Minnesota’s adult moose die each year, a rate two to three times higher than elsewhere. They’re dying in their prime, when mortality should be extremely low, and at odd times of year—not only in late winter, but also in late summer and January, “when they should be as fat as they come,” Butler says.
Moose rot like no other animal, says Butler, who once euthanized a sick moose and put it in a freezer. “[When] I came in the next day, it was still hot inside and it had started to rot.” Once tissues begin to degrade, so does their value in diagnosing illness. “The whole point is to get there within 24 hours,” she says.
That’s finally possible with the new generation of iridium GPS collars, which track location, communicate via satellite, and send text messages when an animal stops moving.
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|Glenn DelGiudice (above) and Ben Betterly examined the kill site of a moose calf in June. They found stomach contents, a few bones, and the radio collar, still transmitting.
Photographs by Greg Breining.
It happened more than 100 times last winter in northern Minnesota. From the open door of a low-swinging helicopter, a gunner would lean out and shoot a tranquilizer dart into a galloping moose. As the animal collapsed in the snow, a team of researchers hustled to their tasks. They took blood and hair samples and measured the moose’s length, girth, and hind leg. Most important, they clasped a radio collar around its neck and inserted a “mortality implant transmitter” the size of a 12-gauge shotgun shell down its throat. Within minutes, the dazed moose would stagger away.
In all, 111 animals were darted and collared, and 28 received the implant transmitters, which lodge in the stomach, monitoring body temperature and activating the collar’s mortality signal the moment the animal’s heart quits beating.
Initial blood samples enabled biologists to identify which of the collared cows were pregnant. GPS updates of an animal’s position in early May showed when a cow made a characteristic beeline of several hundred yards to deliver its calf. After waiting at least 36 hours to allow cow and calf to bond, a helicopter crew located the newborn and, in a four-minute maneuver, slipped on a radio collar, punched in ear tags, sampled blood, and recorded body weight, size, and temperature.
This big production doesn’t come cheap. A few budget items: GPS collars, $259,000; tranquilizing drugs, $33,000; helicopter expenses, $156,000. More than $1 million was spent in the first season. Some $600,000 has come from the Minnesota Environment and Natural Resources Trust Fund (generated by the state lottery). The DNR is paying for the calf study. The nonprofit groups Save Minnesota Moose and the Minnesota Deer Hunters Association have kicked in money. The Fond du Lac Band and 1854 Treaty Authority have bought equipment. And the U’s College of Veterinary Medicine is helping with investigations.
Day or night, the moment a mortality implant transmits a text message, researchers assemble at a rendezvous point and plunge into the woods to locate the downed moose. If the carcass is fresh and near a road, they roll it onto a rubber sled, bundle it into a “moose taco,” and haul it out with a chainsaw winch. If they are too far from a road, they remove the eyeballs, brain, pituitary gland, carotid arteries, and samples of blood, lungs, heart, stomach, kidneys, liver, spleen, adrenal glands, intestines, reproductive tract, femur, and bone marrow. They walk out of the woods with up to 60 pounds of tissue, headed for a refrigerator.
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By the middle of this past summer, 15 adult moose had died—already a higher-than-normal mortality rate. Five were killed by wolves. Two were wounded by wolves and later died from infections. One died from a brain worm infection. Three appear to have died from winter ticks. In the last four cases, Butler is awaiting lab results. “Honestly,” she says, “nothing we’re seeing so far is all that surprising.”
The collared calves, meanwhile, are dying at a furious rate. By late June, only 16 of the original 38 remained. Wolves ate at least six—perhaps nine. Bears got three. One drowned. One was abandoned. One died when, by all appearances, its mother stepped on its head. DelGiudice says he expected a high mortality rate, but it’s frustrating that wolves and bears leave little behind. “We don’t have a carcass to learn from,” he says.
As their investigations continue, Butler and DelGiudice do have hypotheses. They don’t blame climate change, at least not directly. Moose, says Butler, are prospering in warmer climates—the farmlands of Manitoba, the prairies and bottomlands of the Missouri River in North Dakota. Moose are expanding their ranges in New England, even as far south as Boston. “They have a 173 percent higher heat stress index than we do,” says Butler.
Which isn’t to say a changing climate couldn’t kill moose by proxy. For example, mild winters are good for winter ticks, thus bad for moose. Warmer weather might also allow the spread of new pathogens or disease-carrying insects.
Likewise, forest management might play a role. Forest regeneration after clear-cutting produces new browse for moose. But forest openings that are too large might lack adequate shelter and hiding places. Says DelGiudice, “My gut is telling me it’s habitat and the way we cut the forest.” Preventing the fires that burn up duff on the forest floor conceivably creates favorable conditions for the terrestrial snails that carry brain worm.
If predation by wolves and bears appears to be a significant factor, DelGiudice wonders if the DNR would put predator control on the table. “Of course, that would be very controversial, especially with wolves,” he says. In Alaska, game managers kill wolves to protect elk and moose, “and it has an immediate effect.”
So far, necropsies have turned up two new potential moose killers. One is a previously unknown blood parasite that researchers suspect may be transmitted by flies. The other is eastern equine encephalitis, to which horses throughout the Midwest succumbed in decades past. It kills more than 70 percent of the horses it infects, but its effect on moose so far is unknown. Until now, it hadn’t been seen in northeastern Minnesota.
Butler and DelGiudice hope to tease these factors apart as they gather evidence from dead moose, especially in late summer when few moose normally die. Next year, the two plan to dart and collar more moose. They hope for funding for a third year too. Then they’ll follow their collared research subjects for a few more years, until the batteries run down, the collars wear off, or the moose themselves disappear.
In the end, says DelGiudice, “I think we will come up with a pretty good understanding of what’s going on and if there’s anything we can do about it. It’s not going to be just one thing, I guarantee that. Everybody wants to save them.”
The alternative for the heart of the north is heart-wrenching. How much will we miss if the only moose we see on a canoe trip are the photographs in art galleries and the stuffed toys in gift stores?
“Every coffee shop, every bar, every bed and breakfast, there’s something ‘moose,’ ” says Butler. “It’s just embedded in the culture up there. People want to see wolves, bears, and moose. That’s the three things they want to see.”
Greg Breining (B.A. ’74) writes about science, the environment, and related topics. He lives in St. Paul.