Every August, a thick green blanket of toxic algae spreads across the western basin of Lake Erie, threatening fish, drinking water, and the people who live along its shores. Fish can't exactly pack up and leave. But one unassuming resident — the northern map turtle — appears to have figured out a clever escape route, and scientists are delighted about it.
In 2022, University of Toledo herpetologist Dr. Jeanine Refsnider and undergraduate researcher Di'Carlo Jackson glued lightweight acoustic and satellite transmitters to the shells of ten female northern map turtles at a nesting beach in western Lake Erie. The plan was simple: follow the turtles and see where they went. What they found surprised them.
"Since turtles can't swim as fast as fish, it's sort of up to them to be in the right place at the right time," Refsnider noted. The data told a hopeful story. After nesting, all ten turtles headed into open water, but none of them were detected in Lake Erie after late July. By the time the algal bloom peaked in August — its most dangerous moment — the turtles had already moved up into tributaries and nearby marshes, where they overwintered in safety.
"We don't know if they leave because of the algal bloom or if the bloom just coincides with a time of year when they head to a different habitat," Refsnider said, "but it's nice they seem to be relatively safe." She counts that as a genuinely positive discovery, published in the Journal of Great Lakes Research.
The study was also a test of new tracking tools. Acoustic telemetry uses a network of underwater receivers — in this case, anchored throughout the Maumee River and Lake Erie under the Great Lakes Acoustic Telemetry Observation System — to detect signals from transmitters attached to each turtle. Satellite telemetry beams data from specialized devices up to orbiting satellites. It was a "proof of concept," Refsnider explained, and it worked beautifully: acoustic tracking excelled when the turtles were underwater, while satellite tracking caught them once they swam far up a tributary, out of reach of the receivers.
That combination let the researchers map the turtles' full yearly travels, including remarkable treks of 6 to more than 13 miles (10 to more than 21 kilometers) up the tributary. It's a meaningful addition to science, since far more research exists on river turtles than on lake-dwelling ones.
This matters for everyone, not just turtle fans. Harmful algal blooms produce toxins that can sicken people and animals, and understanding how wildlife behaves around them helps researchers protect both. Knowing that these turtles naturally steer clear of the August peak offers a small, hopeful lesson: even in the face of a growing environmental threat, some species have quietly found ways to stay one step ahead. Refsnider and her colleagues plan to keep tracking, eager to learn whether this safe timing holds up year after year.