Research begins to unravel mystery of moose deaths

Wildlife researchers are discovering what's killing Minnesota's moose.

That's more of a discovery than what it seems. Until 2013 when data from the adult moose mortality research project first began flowing in, biologists could do nothing more than say poor health was killing nearly 60 percent of northeastern Minnesota's moose.

Chart showing causes of moose deaths from 2013-2015. Chart data listed in table. Click each chart to see why moose died

Chart showing deaths caused by wolves Chart showing deaths caused by parasites Chart showing deaths caused by infections Chart summarizing all deaths

Causes of moose deaths
2013 2014 2015
Health Wolf Health Wolf Health Wolf
11 9 7 5 13 2

Now – after three years of monitoring live adult moose via satellite, retrieving them as soon after death as possible and carefully examining their remains – those same wildlife biologists can identify specific causes of death.

Preliminary results from 47 of the adult moose captured and collared during the past three years show that two-thirds died from health-related causes. Wolves killed one-third of those moose but sickness in 25 percent of those animals made them easy prey.

Data DNR researchers have collected to date is far from conclusive. Unlike population surveys that utilize statistical models to accurately estimate results, only more data on moose deaths collected over a longer period of time will determine whether the trends researchers are seeing continue.

If they do, researchers can identify specific cause-and-effect aspects to consider when developing wildlife and habitat management actions that potentially could improve moose health and stem the precipitous decline in Minnesota's population.

From the field

Watch a female moose unable to stand because of brainworm

Moose 201, a seven-year-old female collared in 2015, sent a mortality alert on Dec. 31, 2015. The moose had been sending multiple "fake alerts" during the past couple months so local wildlife staff checked and found the moose alive but unable to stand and holding its head off center.

Being New Year's Eve and a holiday weekend, setting up staff support at the University of Minnesota laboratory would have been challenging. So the project's collaborating pathologist at the University of Minnesota, Dr. Arno Wuenchmann, accompanied the mortality team into the field and performed an on-site necropsy.

The moose was unable to move her back end and displayed abnormal neurological behavior. Her body condition was fair and she was pregnant with twin fetuses. There was abnormal hemorrhaging found in her colon and her liver had a moderate-marked liver fluke infection.

Full diagnostics are still pending but the pathologist was able to find evidence of brainworm (P. Tenuis) in the obex of her brain.

What's a MIT?

Concerns about climate change impacts on moose have fueled interest in how these large-bodied animals respond to elevated ambient temperatures. Moose are adapted to survive in cold temperatures; however, increasingly warmer winters have been linked to the moose decline in northwestern Minnesota and may be playing a role in the northeast as well.

A close-up view of a mortality implant transmitter

Researchers have implanted a subset of wild moose in Minnesota with special transmitters that record internal body temperature and transmit this information to their collar. This device, called a mortality implant transmitter (MIT), also is able to record heart activity and send an alert to moose responders if an animal's heart stops beating.

Tracking Minnesota moose

2013 (Year 1)

  • 111 captured (84 females, 27 males)
  • Mean age = 5.8 yrs
  • 83% pregnancy rate
  • 23 MITs deployed

2014 (Year 2)

  • 36 captured (24 females, 12 males)
  • Includes 5 recaptured moose with bad collars
  • Mean age = 5.6yrs
  • 77% pregnancy rate
  • 18 MITs deployed

2015 (Year 3)

  • 32 captured (20 females, 12 males)
  • Includes 1 recaptured moose with bad collar
  • Mean age = 7.3 yrs
  • 89% pregnancy rate
  • 20 MITs deployed


  • Unique individuals in study = 173 (123 female, 50 male)
  • MITs successfully deployed = 61
  • Moose currently being monitored = 74

Moose mortality rates

  • 2015 = 15%
  • 2014 = 12%
  • 2013 = 19%

      Only 8-12% of moose die naturally in Alaska and Canada Chart showing causes of moose deaths from 2013-2015

Moose Research Project 2014


Click above to learn why a multi-year study provides better information and potential answers.

Wildlife Restoration: Your Conservation Dollars At Work


More moose information:


Moose news

Can our moose be saved? (Minneapolis StarTribune)

Minnesota mystery: What's killing the moose? (New York Times)

What's killing Minnesota's moose population? (CBS Evening News with Scott Pelley)

The high-tech detective hunt to save Minnesota's moose (America Tonight, Al-Jazeera America)

Numbers improve but Minnesota moose still not out of the woods (Minnesota Public Radio)

High Tech Research Targets Moose Mortality Mystery (WCCO, Minneapolis-St. Paul, CBS MN)

What's Killing Minnesota's Moose (St. Paul Pioneer Press, St. Paul, MediaNews Group)

Moose hunt canceled; DNR works to answer population decline (KARE, Minneapolis-St. Paul, NBC)