The health of a place can be measured through its longest-lived residents. In Forest Park, those living barometers include many species of turtle.
"These [are] important little creatures," noted Dr. Sharon Deem. "When we learn about the turtle, we learn about the area they're in and what they may have accumulated over decades and decades of life."
A veterinarian, Deem has spent decades studying turtles. This summer, she and other researchers focused on Forest Park, gathering samples to better understand the turtles' health and the impact of plastics on their behavior and diets.
Deem said the study has so far involved "wrangling" more than 50 snapping turtles to test their blood and waste.
The first years of Deem's career took her to the Galápagos Islands, where a native tortoise species can grow to hundreds of pounds and can live for more than a century.
"Originally, looking at the giant tortoises of the Galápagos that we're all familiar with, we didn't even know ... that they have a partial migration. They migrate up and down the volcanoes and within the islands," she said.
Deem eventually left the Galápagos and moved to St. Louis in 2011. She now directs the zoo's Institute for Conservation Medicine. In her new home, she found several new species of turtle to study in Forest Park, including red-eared sliders and snappers that thrive in its many ponds and waterways.
"When we moved here and we're looking at these iconic little creatures in Forest Park, they're sort of like Galápagos tortoises," she continued. "We've learned that many [of Forest Park's turtles] feel kind of boxed-in by roads, sort of like the giant tortoise on an island who is not able to jump into the ocean and swim to the next island … the challenges we have right here in Missouri are some of the same challenges we have in the Galapagos Islands of Ecuador."
Those challenges include the vast amount of plastics that swirl through the air and water in the form of microscopic fragments. With the samples collected in Forest Park, Deem said researchers can begin to understand what happens when these plastics interfere with a turtle's natural development.
"As a field veterinarian, I worked with sea turtles, and I really saw … what plastics were doing to sea turtle populations," she said. "It was during those years that a lot of the [scientific research] was also starting to ask: 'What about the chemicals that make plastics, plastics? Those endocrine-disruptor chemicals?'"
The results from the field tests will take time to analyze, but Deem said the findings won't just provide insights for the turtles of Forest Park. In humans, some studies have already suggested connections between plastics and the endocrine system.
Those connections, Deem said, could explain "earlier puberty in girls, earlier menopause in women, and lower sperm count in men."
While scientists collect samples and test hypotheses, Deem said there are steps people can already take to reduce the amount of plastic in the world.
"At the St. Louis Zoo in 2016, we stopped using plastic bags," she noted. "In 2025, we stopped using single-use plastics. There are great examples of people, both at the grassroots as well as governmental levels, that are really working to make these changes."
To hear the full conversation with Dr. Sharon Deem about testing turtles in Forest Park for plastic, listen to "St. Louis on the Air" on Apple Podcasts, Spotify or YouTube or click the play button below.
"St. Louis on the Air" brings you the stories of St. Louis and the people who live, work and create in our region. The show is produced by Miya Norfleet, Emily Woodbury, Danny Wicentowski, Elaine Cha and Alex Heuer. Layla Halilbasic is our production assistant. The audio engineer is Aaron Doerr.
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