Off-campus South Dakota State University users: To download campus access theses, please use the following link to log into our proxy server with your South Dakota State University ID and password.

Non-South Dakota State University users: Please talk to your librarian about requesting this thesis through interlibrary loan.

Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science


Muskrats (Ondatra zibethicus) and fluctuations of water level are the main forces controlling wetland vegetation cover and composition on a long term basis. IN the absence of artificial water control structures, properly managed muskrat populations are the most natural, long term means of regulating wetland vegetation. Reduction of prairie wetlands has the potential to influence muskrat dispersal patterns and consequently, to reduce the beneficial influences of muskrats on wetland habitats. The objective of this study was to evaluate the changes in seasonal wetlands emergent vegetation cover resulting from experimental manipulation of muskrat populations. Changes in cover of emergent vegetation due to muskrat introductions were difficult to interpret because of major fluctuations in water levels and muskrat populations. During 1986, high precipitation levels influenced emergent vegetation by increasing wetland mean water depth and inundating emergent vegetation. Any reduction of emergent vegetation cover created by manipulation of muskrat population could not be discerned from the effects of flooding. During 1987, extremely low precipitation reduced water levels and increased mean vegetation cover of treatment wetlands between the spring and fall period. Variations in water levels between years also influence muskrat populations, which further complicated the interpretation of the experimental effects. During both years, muskrat densities fluctuated during the experimental period due to dispersal of muskrats into and out of treatment wetlands during the experimental period. There were no significant differences (p>0.05) in emergent vegetation cover between treatments, years, or seasons, the interaction between seasons and treatments was not significant (p>0.05) indicating there was no seasonal change in emergent vegetation cover due to muskrat population manipulation. There was a highly significant interaction between year and seasonal effects (p<0.01), indicating the annual differences in water fluctuations were the controlling factor influencing seasonal changes in wetland vegetation. Indices of muskrat densities varied between treatments and years, and there was a treatment by year interaction (p<0.01), reflecting differences in water levels and public trapping pressure between years. Management implications and future research recommendations are discussed.

Library of Congress Subject Headings

Wetland ecology
Muskrat -- South Dakota
Wetland plants -- South Dakota


Includes bibliographical references (pages 38-41)



Number of Pages



South Dakota State University


No Copyright - Non-Commercial Use Only