MINNEAPOLIS — New data show that researchers at the Department of Natural Resources are beginning to unravel the mystery of what’s killing Minnesota’s moose, they said Tuesday, and a complex interplay of health issues and predators appears to be part of it.
Preliminary results from tracking 173 adult moose that were captured and fitted with GPS radio collars from 2013 to 2015 show that two-thirds of the 47 that later died succumbed to various health problems. Another third were killed by wolves, but 25 percent of those moose had illnesses that made them easy prey, and some that died from health issues had been injured by wolves.
Project leader Glenn DelGiudice cautioned that the results are preliminary and it’ll take six years of data to draw firm conclusions about long-term trends and causes.
The agency launched the project and a related calf study to determine why northeastern Minnesota’s moose population has been on a long-term decline, from an estimated 8,840 in 2006 to 3,450 last winter. Results of the 2016 winter survey likely will be released by late February, DelGiudice said.
The new data give an early picture of what’s causing adult moose to die off, said Michelle Carstensen, the DNR’s wildlife health program supervisor. Health problems appear to be the main reason, she said, while wolves aren’t “the smoking gun.” For example, she said, while wolves killed 16 of the collared adult moose during those three years, they killed only two in 2015.
The researchers are still studying the causes of poor moose health. Fifteen died of parasites such as brainworm, winter ticks or liver flukes. Ten died of infections, four of which were wolf-related. The data also show that nutritional deficiencies and heat stress affect survival. Annual mortality rates ranged from 12 to 19 percent, compared with 8 to 12 percent dying from natural causes in Alaska and Canada.
“Unraveling the complexity takes more time but we’re on it, let me tell you,” Carstensen said.
The researchers are still following 74 adult moose with working collars and hope to recover data from another 20 collars that stopped working, Carstensen said. The devices alert researchers when a moose stops moving, giving them a chance to find the animal and take samples before wolves and scavengers scatter the remains or they decompose.
As recently as Dec. 31, the researchers found a dying moose that was couldn’t stand and had other neurological symptoms. While full test results are pending, the pathologist who performed a field necropsy found evidence of brainworm and liver fluke. The animal was also pregnant with twins.
The DNR had hoped to collar more moose this winter but Gov. Mark Dayton ordered an end it last spring, saying collaring was causing too many of the moose deaths that the researchers are seeking to prevent and too many calves to be abandoned. However, the Grand Portage Band of Chippewa, which isn’t subject to the governor’s order, still plans to collar some moose this winter, Carstensen said.