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 invasio..., Muskrat house density was estimated by collecting aerial imagery at study sites in March 2021 and February 2022 and using the imagery to identify muskrat houses at each site. We used a random-sampling approach whereby a grid of 1-hectare cells was overlaid on each study site and cells that did not represent suitable muskrat habitat were eliminated; from the remaining cells, we randomly selected 10 cells to sample (only a few sites had less than 10 suitable cells, in which case all suitable cells were sampled). Muskrat houses appearing in these random cells were included in the calculation of mean house density in houses per hectare.
Typha x glauca relative abundance was estimated by sampling the Typha community in the field along predetermined transects at each site. Transects were accessed from the water, or in a few cases, on foot. Number of sampled transects ranged from 3 to 7 per site. Each transect was approximately 6 meters in length and was roughly perpendicular to the water's ed..., , # Data for \"Impact of invasive Typha and wetland interspersion on muskrat declines in North America\"

[https://doi.org/10.5061/dryad.v15dv425m](https://doi.org/10.5061/dryad.v15dv425m)

## Description of the data and file structure

Our main response variable was mean muskrat house density which was a proxy for muskrat population density. We estimated the relative abundance of T. x glauca and measured wetland interspersion to test our hypothesis that muskrat populations are declining due to the invasion of T. x glauca and the associated changes to wetland structure. We also determined the mean proportion of open water at each site which may also be impacted by T. x glauca invasions and may thus impact muskrat populations, and we classified each site based on its association with Lake Ontario hydrology, which may further play a role in muskrat abundance.

### Files and variables

#### File: Data\_Melvinetal2024.csv

**Description:** 

This file contains all of the data we used in our ana...