Found throughout most of Canada and the United States, the muskrat is an animal, often resembling but not related to the beaver, that can be found swimming or scurrying along many marshes, lakes, rivers, ponds and streams.

To the native Americans, it was a venerated creature. Several versions of indigenous creation tales, in fact, tell of how a muskrat dove to the bottom of the primordial sea to bring up the mud from which the earth was created, after other animals had failed in the task. For European settlers, naturally, muskrats were principally just looked at as sources of food and clothing.

Today the animals are falling in numbers, and this has conservationists alarmed.

Trappers most notably have witnessed steep declines in their muskrat harvests, often exceeding 50% in some states throughout the animal’s native range. In Pennsylvania, for example, according to the state Game Commission, the muskrat harvest declined from 720,000 in 1983 to 58,295 in 2010.

So why the drop off?

To find out the answer, an investigation headed by the Penn State University College of Agricultural Science was assembled with funding from the Pennsylvania Game Commission and US Geological Survey. Their findings, as reported in Penn State News, were inconclusive, but they did uncover some likely suspects for future consideration:

To analyze trends in muskrat mortality, researchers pored over 131 articles, published from 1915 to 2019, from 27 U.S. states and nine Canadian provinces that contained information about muskrat exposure to diseases and contaminants and mortality events. Information collected from articles included; year of survey; location of survey; methodology; number of animals surveyed; pathogen or contaminant identities; and the presence or absence of associated disease, as evidenced by reported clinical signs or lesions. 

Among the common factors reported associated with muskrat infections or mortality in some cases were: viruses including canine distemper virus, rabies and Aleutian mink disease virus; a variety of fungal infections; ailments such as tularemia and Tyzzer’s disease; cyanobacteria, possibly indicating the presence of toxic algae; parasites including protozoans, trematodes, cestodes, nematodes and ectoparasites such as ticks; toxins, including heavy metals from industrial discharges and lead from ammunition deposits….”

To read the full article in Penn State News, click here.


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