# Marsh Interspersion and Muskrat (Ondatra zibethicus) Habitat Use

## TL;DR

This study investigates whether changes in wetland structure caused by invasive cattails affect muskrat habitat use and population declines.

## Contribution

The study explores the relationship between marsh interspersion and muskrat habitat use in the context of invasive Typha x glauca.

## Key findings

- No correlation was found between marsh interspersion and muskrat habitat use intensity.
- Invasive Typha x glauca may reduce interspersion, but its impact on muskrats remains unclear.
- Further research is needed to understand muskrat population declines.

## 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.

We used camera traps to measure intensity of habitat use by muskrats along a gradient of marsh interspersion to determine whether reduced interspersion, which may be linked to the invasion of
Typha x glauca
, may be contributing to widespread muskrat population declines. Contrary to our prediction, we did not find a correlation between intensity of use and interspersion. More research is needed to determine the cause(s) of widespread muskrat population declines.