The Minnesota Department of Natural Resources moose calf mortality study has documented 25 moose calf deaths to date. The calves, like this one, were captured and fitted with expandable collars when they were at least 36 hours old.
Almost as fast as researchers could fit 49 moose calves with GPS radio collars they were dying. So far, 25 out of 49 calves have perished, 10 by predators.
“Six were killed by wolves, two by bears and two by bears or wolves or some other predator. We couldn’t tell,” said Glenn DelGiudice, Ph.D. who heads up the moose calf study for the Minnesota Department of Natural Resources (DNR).
The collaring took place between May 8 and May 17 in the Arrowhead Region. Scientists captured and fitted the calves with collars that expand as the babies grow. The calves were at least 36 hours old before capture and were found by tracking the expectant mothers who had been collared earlier in 2013.
DelGiudice said two calves died from natural causes, one drowned, and one died from trauma to its head, “It might have been stepped on by its mother. When they get spooked by predators they sometimes accidentally step on their young.”
Eight calves were abandoned by their mothers. “We don’t know why. They might have been young mothers or old mothers, cows in poor physical condition, maybe they couldn’t nurse or were ill or maybe they were affected by the capture/collar efforts. There is always a risk involved with capture. We don’t know. There could be all kinds of things involved,” DelGiudice said.
The calves are monitored every hour. Researchers have two to three computer systems keeping track of the calves, said DelGiudice.
While a calf mortality rate of up to 60 percent is expected, in the last few years the rate has fallen to 70 to 80 percent in Minnesota, not enough to sustain the moose herd. That is one big reason researchers are conducting this study, believed to be the first of its kind. And so far, despite the grim early statistics, DelGiudice said researchers have learned a lot.
“We were shocked at how many sets of twins were born. There were 18 sets of twins, 58 percent of the study. We expected far less than that, maybe 20 to 30 percent.”
Researchers also discovered that calves browse much earlier than believed, and they are getting a first-time look at what baby moose face in the wild.
When signals from the collars indicate calves haven’t moved over a period of several hours, it is assumed that the calf has died and a crew goes in to retrieve it within 24 hours. To date, 15 dead calves have been recovered from the field and are undergoing necropsies back in St. Paul.
“We will be able to determine if they were sick, couldn’t nurse, were just not viable or if this could be attributed to capture,” said DelGiudice.
The Alaskan crew (Quicksilver Inc.) that performed the capture has performed over 600 captures of moose, deer, and caribou, said DelGiudice. “They take extraordinary care not to spook the moose, walking in from quite a distance after spotting the calves and mothers. They try to keep the helicopter away and not frighten the moose.”
Still, said DelGiudice, there has been talk about waiting two to three, maybe four days before collaring calves in the future. And they will look at how better to capture the calves without potentially causing trauma to the mothers. Because the study is so new, everything is up for review, he said.
All of this is part of a larger study to determine what is causing the moose herd to die in northern Minnesota. In 2006 there were almost 9,000 moose in the northern part of the state; today there are fewer than 3,000. Last year there was a drop of 35 percent in the moose herd and the DNR cancelled the bulls-only moose hunt for 2013. In western Minnesota there are fewer than 20 moose, down from over 4,000 in the 1990s.
The DNR is not alone in this $424,000 moose calf study. Helping is the U.S. Forest Service, Fond du Lac, and Grand Portage Band of Lake Superior Chippewa, who assist with the captures and study of adult moose.
This effort dovetails with a $1.2 million mortality study of adult moose conducted by DNR wildlife veterinarian Erika Butler that began in January with the capture and GPS radio collaring of 111 adult moose.
So far scientists have learned many new things about how moose live—and die. Just what isn’t known is if they can figure out how to save the remaining moose—if it is possible to save them—before there are no moose left to study. That, said DelGiudice, is the reason researchers head out into the middle of the forest to bring back a dead moose, or two, as fast as they can.
In fact, DelGiudice said that looking at computer data, it appears a set of twins may have died on Wednesday, June 5, and a crew was on its way to check. He didn’t sound happy when he said it, but there was a quiet resolve in his voice. Researchers will keep trying to get to the bottom of what is killing Minnesota’s majestic moose. There is a lot of work to be done. A lot more to learn. No promises. But the effort will continue.
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