Calling Frog Survey

In the 1960s, the cricket frog was the most common amphibian in Illinois. Today, it has declined from most of the northern counties in Illinois, with a number of possible drivers of decline that may explain its loss. In 2000, Chicago Wilderness initiated a calling frog survey as part of its amphibian biodiversity recovery plan. In 2014, the Calling Frog Survey became part of the Peggy Notebaert Nature Museum of the Chicago Academy of Sciences' roster of community science initiatives.

The overarching goal of the Calling Frog Survey is to establish calling frog survey routes throughout the Chicago region, resulting in amphibian abundance and distribution data. In particular, the Survey aims to continue monitoring sites that have thus far been monitored regularly, so that we can obtain long-term data on regional amphibian trends.

Data from the Calling Frog Survey are shared with land managers and ecologists and are used to guide regional conservation planning and restoration management, to ensure that no other amphibian suffers the fate of the cricket frog.

Dr. Allison Sacerdote-Velat (the director of the Calling Frog Survey) is using the data collected by volunteers to track changes in regional occupancy (the proportion of available habitat occupied) by local frog species, to explore changes in peak call timing over the last two decades.

Data from the Calling Frog Survey were recently used by a Northern Illinois University master’s student, Susan Lawrence, to identify habitat characteristics that promote spring peeper oviposition. She reviewed our data to identify sites that had at least five years of spring peepers with full breeding choruses and nearby sites that lacked spring peepers over a similar length of time. She used the data to identify paired spring peeper and non-peeper sites in several Chicagoland counties and then measured habitat characteristics including pond size, water chemistry, tree canopy openness, and emergent vegetation. She found that canopy openness and amounts of emergent vegetation were greater in the spring peeper sites.

This information will be used by partner agencies to guide additional restoration efforts to promote spring peepers or to improve sites from which they have been lost with canopy closure.

Several partner agencies have used Calling Frog Survey data collected by volunteer monitors as baseline data and follow-up data for habitat restoration grants. The data collected by our program volunteers help provide metrics of restoration success.

First, volunteers are given background on the amphibian life cycle, natural history of the 13 local frog species, and are taught how to identify frog species by the calls and by their physical characteristics. Then, volunteers are taught the survey protocol, how to set up a monitoring route on publicly managed land (forest preserves, park districts, etc.), and the proper conditions for monitoring in the evenings.

After attending these training sessions, volunteers record all frogs and toads they hear along their route on a standardized form and assign a call intensity index for each species heard. They will survey their route at least three times, at least once per observation round. The observation rounds overlap with different species’ breeding periods, allowing volunteers to record the greatest frog species richness (number of distinct species) possible. These observations are then submitted at the end of the season.

Over 100 observe and contribute their data to the Calling Frog Survey per year.