It's still a tough time to be a moose in Minnesota.
Though their numbers show "no significant change" compared to last year, the moose population is still down dramatically from years past, the state Department of Natural Resources said Thursday.
Researchers counted a lot more moose in their 2014 aerial survey - about 4,300 versus 2,700 in 2013. The higher number, however, is likely due to ideal survey conditions, not to a spike in the population, DNR wildlife research manager Lou Cornicelli said.
Heavy snow cover this year made it easy to spot the huge dark animals against an unbroken expanse of white, and there there's always a lot of uncertainty in one year's count, he said.
The long term trends haven't changed, he added. Northern Minnesota's moose counts have fallen by more than half in the past eight years.
"We know we're losing a lot of calves," Cornicelli said. "We know our adult mortality rate is over twice what we see in other places. So we know that the population is still in decline, it can't be increasing at the rates that we're losing animals."
The DNR launched an ambitious first of its kind study last year to try to figure out what's causing moose to die so quickly.
Researchers placed global positioning satellite collars on more than 100 adult moose. When an animal died, in many cases they were able to quickly recover the body to identify what exactly killed it.
Twenty-one percent of adults were killed in the first year. Wolves killed about half; the other deaths were health related, caused by winter ticks, or diseases like brainworm and liver fluke infections, said Michelle Carstensen, the DNR wildlife health program supervisor, who's heading up the project.
Earlier this month, researchers collared an additional 36 moose to replace those killed during the study's first year. In the spring they'll collar 50 more calves, which also died at far higher rates than normal last year. Only about a quarter survived the winter, Carstensen said.
"It's happening in a short time frame. It's extremely rapid," she added. "The impact is dramatic, for the moose that we have. We're still trying to look at what underlying cause might be driving this."
Researchers believe it's related to climate change. Minnesota is at the southern edge of the moose range. Milder winters can stress moose that grow thick coats to survive cold temperatures. Warmer weather also allows more ticks and parasites to survive.
Carstensen, however, said the rapid rate of the moose decline suggests a cause more complex than warmer temperatures alone. In northwest Minnesota, for example, the population crashed from 4,000 to fewer than 100 in less than two decades. "That's a dramatic change for climate change to be the driver."
The population is crashing even faster in northeast Minnesota. The herd there could be gone by 2025, she added.
The moose decline isn't consistent across its southern range. A small population seems stable, for example, in Voyageurs National Park. In Canada, Carstensen says some populations are crashing in Ontario, but growing in Saskatchewan.
Researchers hope to have a much better idea of what's killing Minnesota's moose after three years of the study.
But at that point it may be too late to reverse the decline, the DNR's Cornicelli acknowledged.
"In the end we may just be able to describe what happened, we don't know yet," he added. "At some point we're hoping to translate some of the research findings into management actions, and have a positive benefit on moose."
Those actions could include controlling deer and wolf populations to benefit moose, or creating more moose habitat and forage. Scientists, though, say the first step is figuring out what exactly is causing the moose to disappear.