Relationships Between Muskrat Density and Avian and Anuran Richness in Great Lakes Coastal Wetlands

Abstract

Wetlands in southern Ontario are at risk of degradation and alteration due to human activities. This is a concern because wetlands provide essential habitat for species from a range of taxa, such as birds and anurans (frogs and toads). One wetland-dwelling species whose decline may be linked to loss of wetland wildlife habitat is the muskrat (Ondatra zibethicus). The decline of muskrats may also be linked to declines of other species because muskrats engage in activities that could support taxa such as birds and anurans by increasing habitat heterogeneity. We investigated whether bird and anuran species richness is related to muskrat density or if it is better predicted by land cover variables that describe the wetland and surrounding area at 30 coastal wetlands on Lake Ontario. We estimated bird and anuran species richness using data from the Great Lakes Marsh Monitoring Program and the Great Lakes Coastal Wetland Monitoring Program, and muskrat density based on muskrat house counts. Our results suggest that muskrat activity did not predict richness of anurans or birds overall; however, it did predict richness for the subset of birds that nest in emergent aquatic vegetation. Our results indicate that muskrat abundance in emergent marshes may increase habitat quality for birds that nest in emergent vegetation but may not have a measurable effect on anuran diversity in these same wetlands.