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Moose dying in Minnesota at alarming rate; climate change cited as cause

This bull moose was photographed in Minnesota's Superior National Forest.
This bull moose was photographed in Minnesota's Superior National Forest.

A New York Times piece published this week takes a look at rapidly declining moose populations across the country, with particular attention paid to Minnesota.

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Minnesota has two geographically distinct moose populations, one in the far northwestern part of the state and the other in the arrowhead. According to the NYT, both populations have rapidly declined in recent years. The one in the northwest "has virtually disappeared since the 1990s," the NYT writes, with that population dropping to less than 100 from 4,000. In the arrowhead, the number of moose is declining by 25 percent a year, down to less than 3,000 from 8,000 in the late 1990s. As a result, all moose hunting in the state has been suspended.

The exact cause of the decline remains subject to debate, but experts cite climate change as one of the main factors.

From the NYT:

Several factors are clearly at work. But a common thread in most hypotheses is climate change...

In Minnesota, the leading culprits are brain worms and liver flukes. Both spend part of their life cycles in snails, which thrive in moist environments...

"It's complicated because there's so many pieces of this puzzle that could be impacted by climate change," said Erika Butler, until recently the wildlife veterinarian at the Minnesota Department of Natural Resources.

The hypothesis that rising temperatures in Minnesota are killing off moose is borne out in more detail in an On Earth feature from this summer entitled, "What's Killing Minnesota's Moose?" Here's how writer Jessica Benko answers that question:

Although temperatures are also rising elsewhere in North America, the problem seems to be one of thresholds. Moose are adapted for extreme cold, and Minnesota's North Woods are at the southern boundary of their range on the continent. Researchers in one small study observed moose beginning to pant in order to cool themselves when the temperature rose above just 23 degrees F in winter, when they are carrying a heavy double-layered coat. In summer, temperatures as low as the 60s can cause moose to seek shade. At higher temperatures, their need to keep cool can override their pursuit of the 50 to 70 pounds of food they need to eat each day. The warming trend in Minnesota is bringing an increasing number of days above those thresholds for the moose. There are currently no data to support a direct causal relationship, but some moose biologists suspect stress at critical times of the year may put them at greater risk of dying from predators, parasites, and diseases they might otherwise have been able to fight off.

As the NYT explains, in addition to the whatever intrinsic loss there is to the state when one of its signature species disappears (as well as the loss of tourism dollars), the decline of the Minnesota moose has consequences for other species as well. For instance, when moose browse shrubs, they create habitat for nesting birds.

-- Follow Aaron Rupar on Twitter at @atrupar. Got a tip? Drop him a line at arupar@citypages.com.


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