Marsh interspersion and muskrat (Ondatra zibethicus) habitat use

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
understand the impact of reduced marsh interspersion on fine-scale muskrat
habitat use which will shed more light on broad-scale population trends.
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 marsh interspersion. We
found no correlation between interspersion and intensity of use,
suggesting that factors other than interspersion may drive intensity of
use. The best predictor of intensity of use in our study was the presence
of channelized water features. Our study site, like most marshes in the
region, was highly dominated by *T. *x glauca. Further research is needed
to determine the impact of *T. *x *glauca *invasions on muskrats, as well
as the cause of widespread muskrat declines.