The Tale of the Missing Moose
Air Date: Week of June 1, 2012
The rapid decline of the moose population in the northern Midwest has biologists worried. Host Steve Curwood talks to Seth Moore, the director of Biology and Environment for the Grand Portage Band of Chippewa. Moore says the warmer winters associated with our changing climate are probably related to moose survival rates.
CURWOOD: An average moose stands five to seven feet high and weighs almost a ton. Moose have a very large presence in some of the northern reaches of the United States, and populations are increasing in parts of the Northeast. But recently, wildlife biologists in the Upper Midwest have noticed a severe drop in that region’s moose population.
Joining me from Grand Portage, Minnesota, is Seth Moore. He's the director of Biology and Environment for the Grand Portage Band of Chippewa in Minnesota.
MOORE: We've been seeing a longterm population decline since 1990. We’re seeing lower number of bulls compared to cows, we’re seeing fewer calves on the landscape. So, we’re trying to determine what the causes are for the population decline. We’re concerned that moose are going in the same direction as the polar bear populations in the arctic, and we hope that we can be effective before the population decline has gone too far.
CURWOOD: So, what kind of decline are we talking here? What kind of numbers?
MOORE: It’s pretty significant. It’s over the longterm trend from 1990 to present it looks like about 65 percent of the population has declined. But the scariest thing is that in the most recent survey, one from this year, we showed surveys numbers down from 50 percent. So as a biologist, I have two independent pieces of information to indicate a significant drop in our local moose herd, and I so I need to really take this seriously.
CURWOOD: Now, you work for the Grand Portage band of Chippewa… why is the moose population so important to where you are?
MOORE: Moose are the primary subsistence species to the Grand Portage band. And so, as such, they really define the culture of the band. If we lose the moose population here, we’re losing part of the identity of the Grand Portage band of Chippewa. And so, for this reason, we’re working as hard as we can on this moose population issue, and it’s one of the highest priorities of the Grand Portage Fish and Wildlife Biology Department.
CURWOOD: So, let’s talk about weather and climate. The U.S. had a very mild winter overall. Here in the East, we barely had to lift a snow shovel. What was it like in the far northern Midwest?
MOORE: This last winter, we actually call this a non-winter. We had the lowest snow that we’ve seen in a long time. We didn't really have any cold temperatures, and one of the things about moose is that they’re adapted to a cold climate. So, in winter, moose tend to exhibit heat stress at 20 degrees Fahrenheit. Well, most of our winter was about 20 degrees Fahrenheit, so these animals are stressed out for the entire winter.
We’ve also found here in Grand Portage that our moose populations are correlated with deeper late-winter snow depth. So, deeper late-winter snows means more moose on the landscape, and our Grand Portage weather data has indicated that since 1950, February and March average snow depth has declined by more than 50 percent. In addition to that, our August maximum temperature has increased by about five degrees Fahrenheit over that same time span.
CURWOOD: So, let’s talk about the different hypotheses that you have for what’s happening to the moose population. Heat is obviously one – or rather the lack of cold ¬– and how would that upset those animals?
MOORE: When moose exhibit heat stress, they actually start panting and bed down and really don’t feed at the rate that they need to, to produce calories or make their calves or make milk or even to sustain their own bodies during the winter months. So, heat stress itself is one issue.
There are three separate parasite issues that also affect moose that are related to climate change. One of which is when the snow melts early in the winter, ticks tend to survive. Whereas when we have deeper snow late in the winter, ticks tend not to survive. Winter ticks parasitize moose and cause moose to scrape their hair off during the winter. Sometimes tick loads can exceed 70,000 ticks on a given animal. And when this occurs, the moose is basically replacing its full blood volume in a matter of a couple of months.
The other two parasites that affect moose significantly are brain worms and liver flukes. Both of these are passed by deer, and our deer numbers are high because our winters are less severe. Winter is the population control for deer numbers in this area.
CURWOOD: In nature, and I think Isle Royale which is just offshore of where you are is a classic case of this…moose are held in check or held in balance with wolves.
CURWOOD: What’s happening there in Grand Portage with this with these wild fluctuations in the weather?
MOORE: The thing with wolf populations on the mainland versus Isle Royale is that our wolf populations are correlated significantly with our deer numbers. So when deer numbers are high, wolf numbers are also high. And so, even if wolves are mostly eating deer during their diet, when wolf numbers are high, they’re encountering moose more often, and so we’re also probably getting a little bit of increased predation by wolves, as well, just because deer numbers are high.
CURWOOD: What’s happening with the habitat there that might be affecting the moose?
MOORE: The habitat is changing. And I think that the habitat is changing partly because of the historic wildlife regime has changed and some of the historic logging practices have changed. Both wildfire and logging create new forage for moose that they need. Wildfire was the historic ecological mechanism that this has happened. Logging has replaced that. When wildfire sweeps through an area, it creates new forest. And in addition to that, it also reduces the tick numbers that affect the moose, as well, during the late winter.
CURWOOD: What interventions are you considering that could be implemented?
MOORE: We’re doing a couple of different things. We can reduce some of our wildfire suppression- and this will help control tick numbers and also help to produce young forest. And, the other thing that we can do as natural resource managers, is we can aggressively manage our deer herd to stabilize their population growth.
CURWOOD: Seth Moore is director of Biology and Management for the Grand Portage Band of the Chippewa in Minnesota. Thank you, sir.
MOORE: Thank you. It was great to be here.
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