There are eleven species of frog and one species of toad consistently found in Wisconsin. All of these species can be distinguished by their calls, which are easy to listen for during mating season from early spring into summer. Some species, like wood frogs, chorus frogs, and spring peepers, freeze completely solid during the winter and can start calling soon after melt in early April. Other species, like the green frog and American bullfrog, start later in June and July. This year the American toads had already finished their mating by the time of our field trip on May 20th, but we were just in time for the gray and Cope’s gray tree frogs.

Rori told us that the two tree frog species are practically indistinguishable by appearance alone. The only way to reliably tell them apart is by their calls. The Cope's gray tree frog has a faster, "more insect-like" trill than the slower, "more bird-like" trill of the gray tree frog. Surprisingly, the gray tree frog has twice as many chromosomes as the Cope's gray tree frog, making a blood test the one sure-fire way to identify a physical specimen.

Using a minnow trap provided by the Jessica Hua Lab for the Friends of Amphibians community science initiative, Will Vuyk was also able to find some green frog tadpoles in the Lot 60 marsh. Green frogs overwinter in tadpole form after hatching in July. These ones are likely close to a year old and will soon metamorphose into frogs. One even had visible back legs! Rori explained that the front legs form underneath the skin and can sometimes be felt before they break through. We will be listening close for adult green frog calls in the coming months. The calls sound like the deep thrum of a loose banjo string or large rubber band.