We know a lot about how sea turtles are threatened by our trash, but new research has just uncovered an underreported threat hiding inside lakes and rivers.
“So what happened is: I started cutting open these specimens that had been preserved and sitting in the museum collection for five or six years. I took a Dremel tool, cut off the shell, opened it up, looked at the stomach contents. And I was shocked to find that in the 10 animals that I looked, two of those 10 animals had plastics in their stomachs.”
Greg Pauly’s original plan was to compare the diets of western pond turtles, native to the creeks of the U.C. Davis Arboretum, with those of red-eared sliders that have been introduced. But that all changed when the herpetologist, from the Urban Nature Research Center at the Natural History Museum of Los Angeles County began to look inside the sliders.
“And suddenly I thought, ‘Oh man, there’s a much bigger story here,’ which is that they’re ingesting plastics, and we know almost nothing about plastic ingestion in freshwater turtles. We know it’s a huge issue in marine turtles, but no one’s looking at this in freshwater turtles.”
Plastic ingestion has been reported over and over again in each of the world’s seven types of sea turtles.
But there’s another 352 types of turtles, and only five studies have ever concerned themselves with plastic ingestion in those species. That'’ despite the fact that more than half of all turtle species are considered threatened with extinction. Turtles are among the most imperiled groups of animals on Earth.
“Freshwater turtles around the world are declining. So researchers aren’t going out and euthanizing turtles and putting them into museum collections on a regular basis. We do that for lots of other species, but people aren’t going to be doing that for turtles because it’s just not the right thing to do from a conservation perspective.”
Red-eared sliders are native to the southern U.S. and northern Mexico, but because they’re so popular in the pet trade, they’ve become invasive on every continent except for Antarctica.
As conservationists remove red-eared sliders from natural ecosystems, researchers like Pauly can study them as proxies for native species. By seeing how much plastic the red-eared sliders from the U.C. Davis Arboretum are swallowing, he can get an idea for how much plastic the native western pond turtles may be ingesting as well.
The researchers found bits of plastic in five of 65 turtles, or 8 percent. They used a technique called Raman spectroscopy to confirm that it really was plastic and not, say, bits of crayfish exoskeletons.
“That’s what allowed us to determine that one of the plastics was a nitrile glove.”
They also identified bits of plastic shopping bags and chunks of plastic cutlery. The results were published in the journal Scientific Reports. [Adam G. Clause et al., Plastic ingestion by freshwater turtles: a review and call to action]
“There’s not this awareness that freshwater turtles have this potential threat of plastic ingestion. One of the big goals that we have with our paper is just trying to get increased awareness that plastic ingestion is potentially a big issue for freshwater turtles. If a researcher comes across a dead turtle or a veterinarian is presented with a dead turtle, it’s an opportunity to examine those animals to see whether plastic ingestion is much more common.”
If there’s good news, it’s that none of the turtles that Pauly’s team examined seemed to have suffered from swallowing the litter. They all appeared to be in good health.
“We’re not here saying this is the newest, most horrible threat to freshwater turtles. It’s probably still the case that loss of habitat, introduced predators, overexploitation, those are the big threats to freshwater turtles. But it might very well be that ingestion of plastics and other litter is a big threat for some species and for some populations. We don’t know. But given that turtles are really having a rough go of it right now, this is the most threatened group of vertebrates. Sixty-one percent of all turtle species are threatened or have gone extinct. It’s a rough time to be a turtle on this planet.”
Pauly and his colleagues call on biologists to devote some of their attention to this understudied topic. And regular people can do their part as well, especially with all the single-use PPE we’ve all been wearing throughout the pandemic—like the nitrile glove pieces Pauly found inside one of the turtles.
“It’s really easy to do: limit the amount of single-use plastics that you yourself are even purchasing. Try to make sure that those plastics that you do purchase end up getting reused or recycled and certainly make sure that those plastics don’t end up in the environment.”
[The above text is a transcript of this podcast.]