Frogs & Toads in the Watershed

During 2019 and 2020, VLAWMO made it a priority to better understand our wetlands in a variety of ways. One way we did that was by conducting a frog and toad call survey. The survey is modeled after a long-running MN DNR sampling program and follows the same protocol. A survey consists of 3 separate sampling sessions, or runs, of an established route. In our area, Run 1 takes place between April 15-30, Run 2 takes place between May 20-June 5, and Run 3 takes place between June 25-July 10. Runs begin later in the northern part of the state because frogs and toads start calling later there.

A survey run begins at least 30 minutes after sunset. Warm, still, cloudy evenings are ideal, and a light rain is acceptable. Runs are not conducted if the wind speed is above 8 mph. Loud vehicle noise can obscure calls, so vehicles passing are noted. An observer listens for 5 minutes and counts all frog and toad calls that they hear. An index value is used. This allows a standardized rating of call intensity (ranging from a 1-3 possible score). We heard 8 species in the Vadnais Lake Area Watershed during our survey in 2019. We heard the same species in 2020, with some slight differences at specific locations. A single year of survey would only provide a snapshot of frog and toad diversity. With 2 years of data, we have a more solid baseline to use as we build projects and continue to manage these areas.

Audio description: The first sound that tends to jump out for people in this recording is the high-pitched call of the Spring peeper. These frogs are surprisingly loud for their tiny size. They are also declining in metro areas because of habitat loss, especially wooded wetlands that only hold water for part of the year. Next, find the Boreal chorus frogs. Their call is often described as running a finger along a comb. Then notice the lower pitched, kind of grumbling persistent calls, like they’re doing a lot of gossiping. These calls are made by Wood frogs and are fairly continuous in this recording. Wood frogs have a distinctive black mask. They move from wetland areas to upland habitats after breeding. Connected areas between wetlands and forested areas are important for this species. They overwinter in the leaf litter in upland areas and travel back to wetlands in the spring to breed.

Audio description: This recording is a little quieter than the first one. You may want to adjust your volume as you listen. Boreal chorus frogs (that sound like running your finger down a comb) and Spring peepers (loud single peeps) are present again. It's a little later in the season, so now we also hear the long, steady trill of the American toad, and the loud fluttery trill of Gray treefrogs. In this example, you can hear that the Gray treefrogs are farther off in the distance and have a strong chorus. You may not be able to separate Cope’s gray treefrogs standing out with all of the other noise. You will be able to hear them better in the next recording.

Audio description: These calls were recorded at the small wetland area at the entrance of Tamarack Nature Center. Here you can clearly hear the higher-pitched, melodic trill of the Gray treefrog. Listen for another call that sounds similar, but is faster and lower pitched. That’s the Cope’s gray treefrog. American toads come in around 15 seconds with their sustained trill. Boreal chorus frogs are clear and easy to distinguish in this recording.

VLAWMO conducted frog and toad surveys in 2019-2020. We conducted 2 years of surveys to build solid baseline data. We will use these baseline data to learn more about our projects and resulting environmental improvements in the watershed over time.