UMD and NRRI Seek Answers to Rapid Moose Population Decline
The northeastern Minnesota moose population is in danger, and the University of Minnesota Duluth (UMD) and its Natural Resources Research Institute (NRRI) along with county, state, tribal, and Federal agencies, are working hard to determine the cause of the decline.
OBSERVATIONS ON THE DIRE SITUATION
The problem is well documented. The most shocking statistic is the low number of moose remaining in Minnesota. UMD biology professor and NRRI scientist Ron Moen said the aerial surveys of moose taken by the Minnesota Department of Natural Resources paint a drastic state. “In the past 8 years, the estimate of the northeast Minnesota moose population has decreased from 8,500 to less than 3,000,” he said.
Another problem is that moose calves are not surviving as well as they used to. “For every 100 cows, about 100 calves are born each year,” said Moen. A decade ago, 40 to 50 percent of the calves would live through January. In recent years, only 20 to 30 percent of calves made it that long.” Adult moose are also dying at an unusually high rate compared to other moose populations. “The high mortality rate in both adult and calf moose is too high to sustain the population,” said Moen.
The moose are moving north. Only ten years ago, moose were seen in the Pequaywan Lake area and even closer, about 15 miles north of Duluth. “I used to see them regularly,” said Moen. I haven’t seen a moose that close to Duluth in years, although we do get occasional reports from the Fox Farm road area.” Now, the southernmost edge of sightings is about 25 miles north of Two Harbors, about 10 miles further north than in the past.
EXPLORING EVERY ANGLE
The situation is tragic, and UMD is teaming up with numerous organizations to research the problem from every possible angle. Undergraduate and grad students, along with faculty and researchers, have taken on nearly a dozen approaches. SEE NRRI and Minnesota Moose Research List. They are looking for optimal habitat from the macro and the micro perspective, from viewing aerial photographs and satellite imagery, to measuring moose feeding in foraging areas. Other students are examining wolf scat, collaring and tracking moose, and recovering moose remains to identify cause of death.
Moen is working with NRRI scientist Richard Barnes to map the state’s moose habitats using LiDAR imagery from low-flying airplanes. LiDAR (the name comes from the combination of ‘light’ and ‘radar’) is a method of high-resolution mapmaking that in this case, detects the density of vegetation. Moen will use the LiDAR maps to find habitat conducive to a healthy moose population. “Moose need the low growing shrubs and young trees found in relatively open areas,” Moen said. “Logging, fire, and tree blow downs create good habitat for moose to forage in.” As forests grow old light is unable to penetrate the canopy, and aspen, paper birch, mountain ash, willows, red-osier dogwood, and beaked hazel that moose feed on less available. Moose also need the old forests for thermal cover.
Rachel Ward, an M.S. graduate student in the Integrated Biosciences Program (IBS) working at NRRI, is also identifying characteristics of places where moose live and forage. Ward drives to known moose habitats in wooded areas to document the plant species growing there. Ward and her team have developed a new method of measuring food availability and use. "We have been able to determine diet composition and which plant species moose prefer or avoid," said Ward. In a later part of the study, the data will help her determine how much biomass moose are taking in during a foraging bout and if there is enough food in the forest for moose. Amanda McGraw, a Ph.D. student in the IBS program, will expand on this work in a project funded by the Environment and Natural Resources Trust Fund.
UMD is working on Isle Royale as well. For five decades, Michigan Tech and the National Park Service have been studying the moose/wolf interaction on this remote wilderness island in a famous study that began in the 1960's. Moen is collaborating with Dr. Lee Frelich in the Forest Resources Department at the UM-Twin Cities to measure temperatures in Isle Royale forests. The temperature measurements will be used to predict future forest composition on Isle Royale in a climate change adaptation project, and to predict the effect on plant species that moose feed on.
THE PREDATOR: WOLVES
Yvette Ibrahim, an M.S. graduate student in the IBS Program, is examining wolf scat to see what they are eating. Her project will help answer the question of how many moose calves are being eaten by wolves. Wolves in Minnesota primarily eat deer, moose, and beaver.
Brian Kot, a post-doc scientist with the Minnesota Zoo working under Moen, will be taking a different approach. He is outfitting wolves with GPS collars and following them to their kill and feeding sites. Unlike Ibrahim's project, Kot's will be able to follow the same packs of wolves throughout the year to identify prey species composition.
HEAT AND PARASITES
Kimberly VanderWaal is also a post-doc with the Minnesota Zoo working under Moen. VanderWaal will be studying interactions between deer and moose, especially the parasites they both carry, liver flukes, and brain worm. As climate change progresses and the Northland grows warmer, deer populations will likely increase while moose will face increasing heat stress. The deer pose a far more insidious threat to moose — they pass on diseases, ticks and parasites. Deer populations host parasites such as liver flukes and brain worm with minimal effects. When these deer parasites infect moose, however, the moose become sick or weakened and may die from the infection or from predation.
Winter ticks pose a specific threat. If a moose is bitten by too many ticks, it becomes weak and death can occur. UMD M.S. graduate student Juliann Terry's work is with winter ticks, an insect that spends its whole life on one animal. Terry is visiting bed sites from this spring (based on GPS collared moose) to sample ticks. Since fire has been used elsewhere to reduce other tick species, her project also looks to see how fires affect the winter tick and their habitat.
Tim Cyr's M.S. research takes a different slant. P.tenuis is a parasitic nematode that has different parts of its life cycle in moose or white-tailed deer and gastropods (snails and slugs). The parasite causes brain diseases in moose and can kill infected moose. Cyr is collecting snails and slugs in different Northeastern Minnesota habitats and testing them for the parasite's larvae. He is trying to determine the likelihood of moose accidentally eating an infected snail and becoming sick.
LESSONS FROM GPS COLLARS
UMD graduate student William Chen is a long-time contributor to the moose recovery efforts. “Three years ago, I began developing a computer model to track individual moose,” said Chen. Preliminary work on the model began in 2010, but the model is still in development. “The GPS collar on a moose gets a new location every twenty minutes, and from that we can track each individual moose, and see their movements over time,” said Chen.
The Minnesota DNR is leading two other research projects on moose. One of the most recent developments is a new type of collar, which allows for quick response times upon moose’s death. “The goal of the study is to find out why the moose population is declining.” Chen said. “The old collars wouldn’t send a signal until the moose didn’t move for 12 hours.” A lot can happen in that time. The new collars have sensors for heart activity and are directly connected to researchers’ cell phones. Now, the DNR field teams are notified immediately when a moose dies and can get to the carcass in less than 24 hours.
PULLING THE DATA TOGETHER
“There is no one reason for the unprecedented decline in the adult and young moose population,” said Moen. Disappearing habitat, deer encroachment on habitat, increased parasite populations, sustained warmer weather, and predators all take a toll on the population. “Individually, any one of these factors wouldn’t be enough to cause such a major problem, but coming all at once, they are taking a serious toll on the moose,” said Moen. “At UMD, we are doing our best to provide research that will aid the people of Minnesota and the concerned agencies in implementing a solution.”
NRRI and Minnesota Moose Research Webpage
UMD/NRRI Minnesota Moose Research List
Story by Zach Lunderberg and Cheryl Reitan, October, 2013.
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Cheryl Reitan, firstname.lastname@example.org