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Muskrat population suffers drastic decline

| Tuesday, Sept. 28, 2010

There was a time when muskrats were the foundation on which many a trapping career was built.

Things are not necessarily that way anymore.

In 1983, trappers in Pennsylvania harvested 575,520 muskrats, according to Pennsylvania Game Commission statistics. A year later they took a modern-day record of 621,111.

Then something happened.

Harvests began falling on an almost annual basis, settling at 74,059 in 2008, the last year for which statistics are available.

That's not completely unusual. The take of other furbearing species, like raccoons, red and gray foxes and opossums, has declined, too.

But when it comes to muskrats, what's alarming is that the proportion of juvenile animals in the harvest has been falling consistently, indicating that there are fewer muskrats, said Matt Lovallo, the commission's chief furbearer biologist. It's not just Pennsylvania experiencing that, either; the same is true throughout the Mid-Atlantic and Northeast, he said.

"Populations aren't still dropping. They're at rock bottom. And they don't seem to be doing any better," Lovallo said.

Why that's true is a mystery.

The number of muskrat trappers in Pennsylvania has remained about the same during the past 20 years, noted Cal DuBrock, chief of the commission's bureau of wildlife management.

Fur prices don't seem to be to blame, either. With many species, harvests follow prices, Lovallo said. When a particular type of pelt is commercially valuable, trappers target that animal. When prices fall, they switch to something else.

"When it come to muskrats, that relationship just falls apart. The market for muskrats is better than it's ever been, but we're not seeing the harvest overall or in catch per unit effort," Lovallo said.

"It doesn't matter what the pelt price is, there just aren't muskrats to be caught."

Researcher Nathan Roberts of the Natural Resources Department at Cornell University's will publish a paper in "Northeastern Naturalist" that concludes muskrats indeed seem to be in trouble.

"Numerous anecdotal sources suggest that muskrat densities have declined at sites once inhabited by thriving populations and that little population expansion has occurred into previously uninhabited areas, despite their ability to rapidly colonize previous uninhabited areas," he wrote in that document.

But he can't say why that is, either. He eliminates pelt prices and regular, periodic population fluctuations as possibilities, but said more studies need to be done before anyone can conclude anything beyond that.

"Given the tenuous strength of our supporting evidence, we suggest that further research regarding muskrat population status and potential decline in Eastern North America is justified," he wrote.

"There are probably more questions than answers right now," DuBrock agreed.

Additional Information:

The muskrat file

» Size: Adult muskrat are 22 to 25 inches in length, including an 8- to 12-inch tail that's flat, scaly and mostly hairless. They weigh 2 to 3 pounds.

» Range: Muskrats are one of the most widely distributed furbearers in North America. They occupy almost every type of aquatic freshwater habitat and are often the dominant herbivore in each.

» Homes: Muskrats burrow into stream banks, dikes and dams, often doing considerable damage, but they can also build lodges similar to those of beavers.

» Name: Muskrats take their name in part from the musk, or scent, they leave in likely places in their unique territory to attract mates.

» Importance: Muskrats are pollution sensitive, and as such can serve as indicators of ecosystem health.

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