Frogging in Mississippi National River and Recreation Area

Photo credit: National Park Service

By Nancy Duncan, Natural Resource Program Manager, Mississippi National River and Recreation Area

Originally published in our Fall/Winter 2016-17 print newsletter

A member of the tree frog family, the tiny, non-climbing Blanchard’s cricket frogs (Acris crepitans blanchardi) are considered threatened or endangered in several states in the upper Midwest, including Minnesota, Michigan, and Wisconsin. These small, darkly colored frogs have a very distinctive call, sounding much like someone clinking two pebbles or metal balls together. They are found along rivers, lakes, streams, and ponds, and they overwinter under leaf litter, rocks, and logs near water. Similar to other frogs, these are assumed to partially freeze—from 40 to 70 percent or more of their bodies—during winter hibernation.

While analyzing the 2014 frog song meter acoustic data collected for the National Park Service, researchers detected several Blanchard’s cricket frogs calling in the Mississippi National River and Recreation Area. Three samples containing identifiable cricket frogs were heard and later confirmed by 2-3 expert observers. The site where these frogs were recorded is a dynamic floodplain forest with ponds, a stream, and some wetlands. Fluctuating water levels at the site provided exposed mudflats during low water, which is beneficial for these frogs.

Because cricket frogs are state endangered in Minnesota, a visual confirmation was desired. We visited the site in late summer 2015 to evaluate the habitat and search for the frogs. While the habitat was suitable, no frogs were observed on these late season visits so we decided to conduct more visual surveys in 2016 to see if we could locate additional populations. Last summer we had a frog researcher and a Macalester College intern out scouting likely locations to listen for cricket frogs. So far we have found a number of other frogs within 15 miles of the original site. The researcher is unsure whether these new populations are all part of a large, meta-population, or if these are unique, new populations. Further work is needed to determine this. Meanwhile, it has been exciting to discover that the riverway has a number of new areas where these tiny amphibians exist.