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Voyageurs Park moose providing clues to decline

VNP’s moose herd may yield clues to the puzzling decline of moose in northern Minnesota

Posted 11/7/10

A total of eleven radio-collared moose within Voyageurs National Park are giving researchers better insights into how the state’s largest mammal uses its northern forest habitat. That, researchers …

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Voyageurs Park moose providing clues to decline

VNP’s moose herd may yield clues to the puzzling decline of moose in northern Minnesota

Posted

A total of eleven radio-collared moose within Voyageurs National Park are giving researchers better insights into how the state’s largest mammal uses its northern forest habitat. That, researchers say, may give them a clearer understanding of why this northwoods icon is on the decline in the state.

The research, a joint partnership between the National Park Service, the US Geological Service and the Natural Resources Research Institute, based in Duluth, is taking advantage of recent improvements in tracking technology to gain a far more detailed look at moose movements than has ever been possible before.

Steve Windels, a Park Service biologist, said researchers hope to test several hypotheses that could be behind the decline in moose numbers.

Many wildlife biologists have been pointing to climate change as one major factor behind the decline in Minnesota’s moose population. But researchers recognize that moose research has been unable to make that link definitively, in part because moose populations in other parts of their US range are stable or increasing. Indeed, at a time when Minnesota’s moose population has crashed in the northwestern part of the state, and is declining in the northeast, moose numbers are rising on the prairies of North Dakota, in the Rocky Mountains, and in many part of New England. For now, the moose population in Voyageurs appears to be holding its own. Based on aerial surveys, park officials put the moose population within park boundaries at between 60 and 100.

Researchers acknowledge that climate change may be only one of several factors that are combining in Minnesota to the detriment of moose. That’s why so many researchers have turned their attention to the animal in recent years.

Windels and other researchers believe that only by gaining a much more detailed understanding of how moose behave within their environment, can they begin to determine whether factors like climate change and forest management may be affecting moose. “That’s one of the things this project was set up to do,” said Windels. “To see how moose respond to temperatures. Do they use different types of habitats?”

For researchers, the availability of GPS technology has made this kind of detailed analysis possible. In the past, researchers placed radio collars on animals and would have to use airplanes every few days to fly over the target animal’s home range hoping to get a general idea of its location at that one point in time. “All you would get out of that is one data point,” said Windels.

The new breed of radio collar gathers location data every fifteen minutes, and uploads it automatically to a website, giving researchers many times more data points in a typical week, as well as much more precise information on location. In that past, radio telemetry might have narrowed an animal’s location to a forty-acre parcel. Now, researchers can narrow it much more than that, giving them a much clearer picture of the kinds of habitat moose use, especially when the weather gets warm, as it does more frequently these days.

“Under warm temperatures, when moose are feeling the heat so to speak, do they change their activity levels?” asked Windels. “Do they bed down more and feed less? Are they using certain habitat types more than others? Are they spending more time in spruce bogs, or in beaver ponds? We’re hoping to find out the array of temperatures out there on the landscape, and are moose using them to stay cool,” said Windels.

While cold temperatures are often a limiting factor for many animals, moose are actually well-adapted to cold temperatures, say researchers, so it may actually be the prevalence of warmer weather that is creating stress for the population.

Researchers suspect it’s more than just warming temperatures affecting moose in Minnesota. DNR researchers have been gathering blood and tissue samples to examine the effects of disease and parasites, particularly liver flukes and brainworm, on the moose population. According to DNR research veterinarian Erica Butler, brainworms are present in a relatively small percentage of the moose brains they’ve obtained from hunters, but liver damage from flukes appears more widespread. Both the brainworm and liver flukes are carried by whitetail deer, and are passed on to moose through land snails, which serve as an intermediate host.

Researchers are also asking for blood samples this year, which they can use to determine the liver function of harvested moose as well as screen for other parasites.

In addition to parasites and disease, genetic factors may be at work. The Minnesota moose herd is contiguous with and likely shares similar genetics with moose in northwestern Ontario, a population that has adapted to some of the coldest wintertime temperatures found on the continent. That could make the Minnesota moose population more susceptible to the negative effects of a warming climate, compared to moose native to milder climates, like those found in the Rockies or New England. “Those populations don’t appear to be affected by temperatures as much,” said Windels.

Voyageurs a valuable laboratory

While moose research is ongoing outside of Voyageurs, the park itself offers an interesting location to test how factors such as forest management may be affecting moose. While much of the park’s main land mass was logged in the past, the forest has now had nearly 40 years to mature. That means the park’s forest composition is significantly different most areas outside the park, which are now dominated by younger, more recently harvested timber.

If moose are better able to hold their own in the park, it could be a sign that forest management practices have contributed to the problems faced by moose.

While researchers are considering such questions, for now they’re not offering any conclusions. They plan to continue their research at least until 2013, at which point the data may yield some clearer answers.

Collaring moose a risky business

Convincing wild animals weighing as much as 1,000 pounds to wear radio collars isn’t an easy task. In fact, it’s one that’s largely left to expert contractors, like Idaho-based Leading Edge Aviation, which specializes in animal capture using nets and ropes, rather than tranquilizers.

The Voyageurs research team turned to Leading Edge back in February, when it fitted collars on moose. Using helicopters, the company locates target moose and herds them into open areas, where they deploy special guns, that shoot a net over the animal. Once entangled, Leading Edge personnel, many of whom work as cowboys much of the year, drop from the helicopter and lasso the animal’s legs, before tipping it on its side, where the animal is blindfolded. Once blindfolded, the animals are surprisingly docile, said Windels.

While the capture method is generally seen as lower risk for the animals than using tranquilizers, it’s not without its dangers. The stress from the capture can be significant. Indeed, one of the ten female moose captured in Voyageurs in February died a week later, possibly from stress-related causes.

Researchers hope the collared moose won’t experience as much stress the second time around. Windels said the target moose will be recaptured this winter and fitted with a new collar, one that won’t need to be replaced for two years. In addition to the 11 moose already collared, researchers hope to add eight more moose to the radio-collared sample population.