Volunteers with Iowa’s frog and toad survey have been collecting important information for more than 35 years, documenting population trends, identifying places with data gaps, and how changing land use and fluctuating levels of precipitation impacts the amphibians. They’ll be headed out again this year starting on April 1.
The 2025 survey results are posted on the Iowa Department of Natural Resources (DNR) website at www.iowadnr.gov then type Frog and Toad Survey in the search box.
“This survey would not be possible without an army of volunteers over the years,” said Stephanie Shepherd, wildlife biologist with the Iowa DNR.
Since the standard survey began in 1991, more than 600 volunteers surveyed 2,371 sites across 96 of Iowa’s 99 counties. Collectively, they made more than 45,000 visits to these sites on 7,146 nights.
The 2025 survey results followed recent trends - bullfrogs, green frogs and cricket frogs have been slightly increasing, and American toads, eastern gray treefrogs and spring peepers have been slightly decreasing. The most common species recorded were chorus frogs, American toads, cricket frogs and eastern gray treefrogs. The call survey is the only way to tell the difference between two species of gray treefrogs outside of a laboratory.
The data is used for species distribution and to look at population trends across time, looking at the percentage of wetlands where X species occur.
“We also want to know where the frogs aren’t, hearing no frogs at an area that looks ‘froggy’ is also important data,” she said. “We are looking for more data on the range-restricted species that are mostly on the ‘coasts.’”
Shepherd said 140 monitors participated last year, including 33 new volunteers. Volunteers are required to attend a training session where they learn about the routes, what data to record and spend much of the time listening and learning each of the calls. They receive digital audio files for review to help with call recognition.
Surveys take place at night. Volunteers drive their route beginning 30 minutes after sunset, stopping at between five and 10 sites. At each site, they turn off the car, get out and listen at the side of the road for five minutes and record the different species heard. The route must be completed by 1 a.m.
Routes are repeated three times: once from April 1 – May 1; once from May 7 – June 7; and once from June 13 – July 13; to capture each singing chronology.
Three volunteers have been involved since the beginning in 1991, 10-12 people have volunteered for 30 years or more and 25 people have volunteered for more than 20 years, she said. The average number of years volunteers participate is five.
“If volunteers stick with it, then they usually volunteer for a number of years. If you’re interested, try it out, if it’s not for you, that’s okay,” she said.
The frog and toad survey is one of the community science opportunities at the Iowa DNR where the public can participate, alongside the bald eagle, peregrine falcon and osprey nest monitoring, the bumble bee atlas, the acoustic bat survey in partnership with Iowa State, and the new firefly survey that the DNR is not coordinating, but helping to promote.