Abstract
Muskrat (Ondatra zibethicus) populations have been declining in North America for decades. The precise cause of these widespread declines has not yet been identified. Over a similar timeframe, wetlands across large regions of North America have been experiencing an invasion of hybrid cattail Typha x glauca. This invasion is associated with many negative consequences for wetlands, including a reduction in biodiversity, open water habitat, and interspersion of water and vegetation. Muskrats are strongly tied to wetlands, especially where there is a high degree of interspersion of water and emergent vegetation. Therefore, a widespread reduction in interspersion caused by T. x glauca invasions may be contributing to widespread muskrat population declines. We sought to better understand the impact of marsh interspersion on fine-scale muskrat habitat use in light of widespread invasions of T. x glauca. We measured intensity of habitat use by muskrats in a large, Typha-dominated marsh in south-central Ontario using camera traps, stratifying camera placement along a gradient of interspersion. We found no correlation between interspersion and intensity of use. The ubiquity of T. x glauca and low overall interspersion at our study site may have prevented a robust test of our hypothesis. Further research is needed to determine precisely how interspersion affects muskrat habitat use at a fine scale, and how potential changes in habitat quality and use may be contributing to widespread muskrat population declines.