Occurrence patterns and trends of frogs in coastal wetlands of the Great Lakes call for further habitat restoration

Countless wetlands have been lost and degraded globally making amphibians the most threatened vertebrate class. However, despite facing extensive threats and stressors, coastal wetlands of the Laurentian Great Lakes of North America (lakes Superior, Michigan, Huron, Erie, and Ontario) still support sizable populations of frogs (order Anura, including toads). We used data from the Great Lakes Coastal Wetland Monitoring Program to quantify the first-ever annual occurrence probabilities and trends (2011–2023) of eight marsh-breeding frog species, or groups of species, at 1,550 point count locations in 747 coastal wetlands throughout the Great Lakes, and to assess 11 potential drivers of occurrence. Across our study area, Green Frog (Lithobates clamitans) occurrence increased by 8% per year, whereas Chorus Frog (Pseudacris maculata, P. triseriata) occurrence decreased by 14% per year. We found more positive or stable trends among lakes and species (85%) than negative trends (15%). Occurrenc..., Study area and design
We surveyed frogs in coastal wetlands throughout the Great Lakes basin (Figure 1). Coastal wetlands were selected according to CWMP protocol using a stratified, random sampling procedure (Uzarski et al. 2017, 2019). Further details regarding the study design are in Burton et al. (2008). The sampling domain included all marshes greater than 4 ha in area with a permanent or periodic surface-water connection to an adjacent Great Lake or their connecting river systems (Uzarski et al. 2017). The selection of wetlands was stratified by 1) wetland hydrogeomorphic type (riverine, lacustrine, barrier protected; Albert et al. 2005), 2) region (northern or southern; Danz et al. 2005), and 3) lake (i.e., the watershed of one of the five Great Lakes). We sampled approximately 20% of all wetlands in each stratum each year, so that nearly all coastal wetlands within the Great Lakes basin meeting the selection criteria were sampled at least once every five years. In addition, we r..., , # Occurrence patterns and trends of frogs in coastal wetlands of the Great Lakes call for further habitat restoration

[https://doi.org/10.5061/dryad.hmgqnk9v8](https://doi.org/10.5061/dryad.hmgqnk9v8)

## Description of the data and file structure

We surveyed frogs in coastal wetlands throughout the Great Lakes basin. Coastal wetlands were selected according to CWMP protocol using a stratified, random sampling procedure. We conducted frog surveys at one to six fixed point count locations at the edge of, or within, each wetland in each year that a wetland was selected for surveys. Point count locations were > 500 m apart to avoid double detections. Each point count location was surveyed for 3 min on each of three occasions at least 15 days apart between late-March and early-July, which is the main breeding season for frogs in the region. We sampled water quality once between mid-June and early-September in each wetland in each year that a wetland was selected for surveys. Three water q...,