Data for: Impact of invasive Typha and wetland interspersion on muskrat declines in North America

Muskrat (Ondatra zibethicus) populations are declining in North America.
The exact cause of these declines is largely unknown. Along a similar
timeframe, wetlands have been experiencing an invasion of cattail (Typha)
throughout the continent. Specifically, T. x glauca, a hybrid of native T.
latifolia and non-native T. angustifolia, has been increasing in range and
abundance. This hybrid is associated with many negative impacts on wetland
ecosystems, including reductions in biodiversity, open water habitat, and
interspersion of water and emergent vegetation, the latter of which is an
important habitat feature for muskrats. We sought to determine the impact
of invasive T. x glauca on muskrat populations. We sampled 39
Typha-dominated marshes in southern Ontario, Canada to test the hypotheses
that muskrats are declining in North America due to: (1) the increased
relative abundance of T. x glauca in marshes, and (2) reduced wetland
interspersion, which is associated with T. x glauca invasions. We
estimated muskrat population density using house counts, sampled Typha
communities to determine the relative abundance of T. x glauca, and
measured interspersion using remote sensing techniques. We found that
muskrat population density was positively associated with interspersion,
but not associated with the relative abundance of T. x glauca. However,
most sites were highly dominated by T. x glauca, limiting our inference.
Our findings suggest that changing wetland structure may be contributing
to muskrat population declines in North America, but more research is
needed to determine the full impact of T. x glauca invasions on muskrat
population declines.