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Attention 4-H Members - Trapping Muskrats in Ohio is a great new project for you to take. Trapping season is a great time to complete this project. Contact your 4-H advisor for more information.

Larry Dishong
The Maplewood Community Fire Department made a donation to OSTA in memory of Larry Dishong.

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Muskrat Study Report

For several decades, trappers in the Midwest and the northeastern United States have been aware that populations of muskrats have been declining and their distribution reduced. Similarly, wildlife managers have recorded declines in muskrat harvests. The overall declines in regional population trends for muskrats are alarming. As such, the Ohio Division of  Wildlife, working in cooperation with the Wilds, launched an ambitious project to methodically examine potential factors that could be contributing to the muskrat decline. Our first step was to examine their health, and determine exposure to toxins and other chemicals. Accordingly, objectives of this study were to collect muskrat carcasses from across Ohio to determine health
in terms of (1) presence of disease, (2) accumulation of toxins, and (3) detrimental effects of contaminants. Sex and age structure, as well as reproductive output were also determined for the sample population. Trappers across Ohio donated legally trapped muskrats for this study. A total of 592 muskrats from the 2013-14 and 2014-15 trapping seasons from across the state
were necropsied.

• The overall declines in regional population trends for muskrats are alarming. As such,
the Ohio Division of Wildlife, working in cooperation with the Ohio State Trappers
Association and the Wilds, launched an ambitious project to methodically examine
potential factors that could be contributing to the muskrat decline. 
• Objectives of this study were to collect muskrat carcasses from across Ohio to
determine health in terms of (1) presence of disease, (2) accumulation of toxins, and (3)
detrimental effects of contaminants. Sex and age structure, as well as reproductive
output were also determined for the sample population. 
• Trappers across Ohio donated legally trapped muskrats for this study. A total of 592
muskrats from the 2013-14 and 2014-15 trapping seasons from across the state were
necropsied.
• Based on molar indices, approximately 11% of the samples were adults. All adult
females had reproduced, having 1–3 litters/year with an average placental scar count of
15.0 ± 6.1 (range 3 – 32). Sex ratio was 1.1 males for every 1.0 female. These values
are typical for muskrats at Ohio’s latitude. 
• Few abnormalities of carcasses were noted during necropsy. White lesions noted on the
livers of six muskrats were diagnosed as strobilocercus, which are bladder-like cystic
structures formed by taenioid tapeworm larva. These likely had little effect on the
population. 
• Pesticides and personal care products appeared to play a minor role in muskrat
toxicology based on observed exposure. 
• Nineteen of the 23 tested elements, however, occurred above threshold values. 
• Forty muskrats of the 41 adults tested exhibited exposure above threshold limits for 1 to
18 metals. 
• Less than 25% of the individuals (n = 9 of 41) were exposed to aluminum, arsenic,
boron, chromium, cobalt, copper, cadmium, lead, nickel, selenium, silver, vanadium, or
zinc. 
• Three muskrats from widely separated areas, Ashland, Fayette, and Guernsey counties,
exhibited exposure to 18, 17, and 18, of the 23 metals for which we tested, respectively.
? The exposure to 6 metals was more widespread and consequently has the potential to
cause detrimental effects on a large scale. These were antimony (n = 19 muskrats),
calcium (n = 19), iron (n = 21), mercury (n = 21), molybdenum (n = 19), and strontium (n
= 22). 
• Muskrats in areas across Ohio suffered from moderate to severe levels of metal
contamination. Such contamination can have negative effects on health, survival, and
reproduction. However, the pathogenic effects of contaminants cannot be known without
additional testing. Histological tests on major organ tissues are needed to determine if
and to what extent contamination with metals is impacting muskrat populations in Ohio.
• Nonetheless, knowledge concerning the level of exposure to toxic metals in Ohio’s
muskrats represents a significant beginning in our effort to determine factors contributing to muskrat decline.
Study Summary
January 12, 2019: OSTA Fur Auction, Bucyrus, OH

February 9: OSTA Fur Auction, Jeffersonville, OH

March 9: OSTA Fur Auction, Kidron, OH

March 23: OSTA Banquet, Waldo, OH
Est. 1940 - The nation's third oldest trapper association
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