DNR suspends moose captures

[Lee Borgersen]

  DNR suspends adult moose captures early..

April 24/ 2015
 
High mortality rate among captured adults still unexplained by researchers
 
 
   
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REGIONAL— Continuing problems with its moose capture operations prompted DNR officials to suspend the collaring of adult moose earlier this winter. The early end to the moose capture effort this year has not been previously reported.

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DNR researchers involved with the project reported earlier this month that they suspended the work of the capture team, conducted in February, after five of the adult moose died in the process.

“We did end it early,” said Michelle Carstensen, the DNR's Wildlife Health Program supervisor. The moose team had hoped to collar 36 adult moose, 30 for the DNR’s ongoing mortality study and six additional for related research being done by biologist Ron Moen, of the Natural Resources Research Institute in Duluth.

The team did capture a total of 32 adult moose, but five of them died due to what’s known as “capture myopathy,” a muscle disorder that most frequently manifests itself following capture or restraint of mammals. In each case, the DNR euthanized the affected moose and sent their carcasses to a DNR lab for analysis.

DNR researchers say they still don’t know why so many of the moose exhibited capture myopathy this year, but they say the tranquilizing drugs used in the capture of adult moose do not play any role in it. “These drugs have been used forever,” said Terry Kreeger, a veterinary specialist also working on the moose project. “There’s nothing that we have done that is different from what anyone else has done. Everybody with any experience in this field at a loss to explain these mortalities,” Kreeger added.

Typically, researchers expect no more than two- or three-percent of animals captured will experience this disorder, and that was the rate the DNR’s moose team experienced during the first two years of their study. This year’s rate of 15 percent is highly unusual, and that’s why it prompted DNR officials to suspend their work.

“We didn’t want to risk additional moose,” said Carstensen.

The high rate of capture-related deaths suggests an underlying condition may be affecting moose in the region. “I have done hundreds of moose captures,” said “We have never seen these kinds of reactions with any other population of moose we’ve worked with,” he said.

The higher rate of capture-related deaths comes despite the fact that the limited snowfall this winter left area moose in relatively good condition. “The males were mostly thin, but that’s not usual because of the fall rut,” said Carstensen. “But the adult cows were in good shape,” she said. Indeed, the DNR reported several of the cow moose captured were extremely large, comparable to the size of moose found in Alaska.

But even normal weight females were among those animals that suffered capture myopathy this year. Indeed, three of the five moose that died were female, including one that was pregnant with female twins and another that was carrying a single male fetus. A third moose cow was not pregnant at the time.

Future of study

in question

Whether the DNR will continue to capture and collar moose next year remains to be seen. In the wake of the April 10 report on problems within the DNR’s moose calf study, Gov. Mark Dayton’s chief spokesperson Matt Swenson said the governor has informed the DNR that he’ll approve no more funding for calf captures after this year.

The DNR had planned to wrap up its calf and adult moose captures this year, but Carstensen said the agency may have sufficient funding left over for more adult captures next year. “At this point, we have two complete years, and we would like to get another full year or possibly two before publishing our results,” said Carstensen. If DNR researchers do attempt additional captures next year, she said the capture team will be sensitive to the issues experienced this year.

Adult survival looks better

Despite problems at the time of capture, the overall story for moose in the region looks somewhat better. While nearly 20 percent of the roughly 100 adult moose in the DNR’s study died in 2013, survival was much improved the following year, with just 11-percent mortality— a rate considered normal for moose in North America. “Coming into 2015, we haven’t really seen much mortality,” said Carstensen. “We had one wolf kill a few weeks ago.” Moose mortality typically peaks in later winter, but with the limited snow cover this year, moose were less susceptible to wolves than in the last two winters.

While the limited snow cover this year may have boosted moose survival, it could well have a downside for moose next winter. That’s because the early disappearance of snow cover and the early warm-up this April is expected to be a boon for winter ticks, which, at times, have become a major plague to moose in the region. “My prediction is they’ll have a heavy tick load next winter,” said Cartensen. Heavy tick loads can cause anemia in moose and it also prompts them to rub against trees in an effort to scrape the ticks off. But that can erode their fur as well, leaving bare patches that make the moose more vulnerable to extreme cold.


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