If you wander by the ponds in the Arboretum in early evening or after a rain, you may hear what resembles a chorus of fine-tooth combs. This is the call of the western chorus frog (Pseudacris maculate), an elusive tree frog found in open, damp areas. During the first run of the Frog and Toad Survey in late April, a team of Carleton naturalists heard western chorus frogs calling en force, especially near Kettle Hole Marsh, Oxbow Pond, and along the Cannon River. These frogs are tiny but mighty: though nocturnal, secretive, and only ¾ -1 ½ inches long, their sharp preep! call can be heard from up to a mile away. During peak breeding season in late April, male chorus frogs sing during both day and night.
Aside from their distinctive call, western chorus frogs play an important role in wetland ecosystems. They are considered an indicator species, meaning that changes in behavior or morphology are often strong indicators of pollution or toxic substances in the environment.
Though it is the most abundant frog species of the Arboretum, the western chorus frog is just one of six frogs that call Carleton home. During the Frog and Toad Survey a few weeks ago, northern leopard frogs (Rana pipiens) also put on a show near Kettle Hole Marsh with their rattling snores and soft grunts. Named for their distinctive circular spots, leopard frogs are found in grasslands, wet meadows, and forest edges. During summer surveys, leopard frogs can be found hunting for small insects in the prairie.
Other frogs of the Arboretum include the gray treefrog, Cope’s gray treefrog, bullfrog, green frog, and wood frog. Next time you walk through the Arboretum, take a moment to pause by the ponds and the Cannon River along the way. The spring chorus is a show you don’t want to miss.