Declines in Muskrat (Ondatra zibethicus) Population Density in Prince Edward Island, Canada

Posted on Oct 30, 2019


by Garry J. GREGORY, Randy DIBBLEE, Pierre-Yves DAOUST, and Michael R. VAN DEN HEUVEL
CWBM 8 (2): 46–60

Correspondence: Mike van den Heuvel, Department of Biology, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, C0A 1C0, Canada.



Muskrats (Ondatra zibethicus) are the most abundant furbearer on Prince Edward Island (PEI) and a cornerstone of the trapping industry in the province. In the past 10-20 yrs, trappers have reported declines in muskrat density in areas that have traditionally been much more productive. In order to evaluate the validity of those concerns, a trapper survey was conducted, historic muskrat harvest data was evaluated, and population characteristics and demographics were directly estimated. Trapper surveys confirmed the general opinion of decreased muskrat density, though only in those trappers with 2 decades or more of experience. The number of trappers and pelt price were significantly positively related to annual harvest, and unemployment negatively related to annual harvest indicating that harvest is influenced by economic factors. Harvest was not significantly related to weather-related metrics during the harvest season. While age/sex ratios in the fall harvest have not changed since the 1960s, mark-recapture studies in 3 marshes found that current population densities ranged from 1 to 5 muskrats/ha, at the lower end of expected densities of muskrats based on studies from throughout North America. Furthermore, muskrat house density in 4 marshes was less than 0.12 house/ha. Those values were generally lower than any reported in the literature, and comparison of house density with data from the 1960s from 1 marsh showed an almost 6-fold reduction in house counts. Overall, these data suggest evidence for low but stable populations of muskrats in the majority of PEI marshes examined, substantiating trapper opinions of low muskrat density.

Key Words: Canada, Decline, Harvest, Mark-recapture, Muskrat, Population, Prince Edward Island, Trapping.



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