Studying Synchronous Fireflies at Congaree National Park

COLUMBIA, S.C. —  A natural phenom that happens once a year went mostly unseen due to the coronavirus. Normally, thousands would watch the synchronous fireflies at the Congaree National Park. This year, nature went on with the show without as many people watching.  

While visitors were kept away, researchers visited the park to study the bugs. The fireflies sync their flashes during a two week period that normally takes place during mid-May and early June. Photurius frontalis is the species that is found at Congaree National Park. It is one of three synchronous firefly species found in North America. 

Dr. David C. Shelley, Chief of Resource Stewardship and Science at Congaree National Park, tells News19 researchers used the days without visitors to get data on the fireflies that may help them better understand their behavior. It “has actually afforded researchers to get in there in these other areas that normally have a lot of visitors and a little bit of background light coming from that and get some data and we’re excited because next year when we have visitors they can come back and see does the presence of those visitors,how does it change or not what is going on,” Shelley says. 

Researchers from the University of Colorado at Boulder spent time at the park making 3D high resolution videos to study how the fireflies act as a group. Shelley says they are also using models from neurology to study how instantaneous they light up. 


“We know nothing about the genetics of this particular firefly,” Shelley says. “A lot of times I think folks take for granted how much scientists know or how much data we have about the natural world. The truth is there’s so much we don’t know and that’s what makes science so exciting. And places like Congaree National Park so important – they are laboratories to understand these things.”

Science also helps the park inform visitors when to visit. Scientists collected data from weather stations and used climate models to help them study when the fireflies came out and their behavior each night. 

Over the past several years, a growing crowd of on-lookers have visited the park to see the phenomenon. Social media has helped create a buzz around the annual event and brought people from across the country to the swamp. About six years ago the park didn’t have staff on hand during the breeding period of the fireflies. Shelley says that changed when rangers noticed “a lot of folks were stepping out and putting lawn chairs and coolers well meaning to enjoy, but they happen to be putting them out in the leaves where the females are.” The park began to put up ropes and signs to keep people around the visitors center to observe the fireflies. 

As crowds grow for the tradition, the park is looking at ways to manage how people congregate and watch the fireflies. Next year, there will likely be a reservation lottery where visitors will need to make an appointment for the night they would like to come and see the light show. Buses may also be used to bring people in and out of the park to limit the amount of disturbances to the environment and manage the crowd size. 

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