A chorus of croaks and calls

When we think of spring, we tend to imagine pleasant weather, an ensemble of bird calls and blooming wildflowers. An oft-forgotten group of organisms, which serves just as reliable an indicator of seasonal change, is that of frogs and toads. These creatures might look small, but they create a mighty force with their calls. On a typical spring night, ponds, streams, wet lands and wooded areas here in North Minneapolis and throughout the Twin Cities, come alive with their symphonies as they compete for mates and territories. Listening closely to the cacophony reveals an enormous variety of vocalizations and illustrates the complex evolution of these species.

Frogs and toads are the most diverse group of amphibians. Minnesota has 11 native frogs and three toad species. Males signal their readiness to mate through loud and repeated advertisement calls to females. The ability to call at such volume comes from their paired throat sacs, which expand with air and act as an amplifying chamber for the noise. While the main purpose is to attract a female, frogs and toads may also use calls to defend their territory. The exact sound produced varies depending on a number of environmental conditions as well as the characteristics of the individual. In fact, frogs and toads from different parts of the state will even have local “dialects,” in which variations occur based on geography. Residents of the Twin Cities metro area are serenaded by seven frog species as well as the American Toad.

Wood Frogs are the first to emerge in the spring after winter dormancy. Breeding begins early in spring, sometimes even before all the ice has melted, in the temporary wetlands that form during this time. Wood Frogs breed explosively, which means all of the mating occurs in huge gatherings of frogs over the course of several days. Their calls resemble a short chuckle, akin to the calls of a duck.

Small and inconspicuous, the next frogs to listen for in early spring are the Chorus Frog and Spring Peeper. Although difficult to see, they are easily heard in the night. Aptly named, the Spring Peeper’s call is a repeated chirrup that rings throughout the spring air. They are quite small, about the size of a paper clip. However, tinier still is the Chorus Frog, Minnesota’s smallest species of frog. Chorus Frog calls are also a familiar sound of the forest, resembling something scraping the toothed end of a comb.

Starting in April and continuing through May, the call of Minnesota’s state amphibian, the Northern Leopard Frog can be heard. Their staccato call begins with a deep rattling snore that lasts 2-3 seconds, followed by a sound like a heavy creaking door slowly open. Compare this with the low monotone exhibited by the Cope’s Gray Treefrog call and the eerie high-pitch shriek of the American Toad starting in May. As summer begins, listen for the cartoonish croaks of the Green Frog, which sound like the pluck of a rubber band being released. The last to join in is the Bullfrog, whose strange call resembles a drone-like buzz straight from a sci-fi film.

If you’re interested in finding out more, sign up for our May 21 program about frogs and toads. Curious about other signs of spring? Visit the Kroening Interpretive Center for resources on the seasonal changes outside. Look for migrating birds as they travel up the Mississippi River Flyway. Borrow a pair of binoculars from the front desk and hit the trails to see what birds have returned, started nesting, or transformed into their spring plumage. Or check out our bird feeding station from the comfort of the Interpretive Center at our viewing windows.

May Free Public Programs (all ages): May 6 – Early Birding: Search for birds while on a naturalist-guided hike, 9-10:30 a.m.  May 13 – Fishy Fun: Meet the native fish in our aquarium, then create some fishy art, 1:30-2:30 p.m.  May 21 – Toads, Frogs and Polliwogs: 1:30-3 p.m. Learn about amphibians and make a toad home for your yard.  Each Saturday, 11 a.m.-3 p.m. – Naturalist’s Nature Table (themes change weekly). Each Sunday, 12:30-3:30 p.m. – Family Funday (themes change weekly)

Summer Camp: Sign up for week long camps to have outdoor adventures all summer! Monday-Friday, 8 a.m.-4 p.m. For ages 6-12. Registration fee $75 Camp starts June 12!

For more info or to register for programs at North Mississippi visit minneapolisparks.org and like us on Facebook to stay in the loop about what’s happening in our park!

Written by Lynn Hu, Minneapolis Park & Recreation Board Naturalist, North Mississippi Regional Park