Sea Turtles Mistake The Odor Of 'Stinky' Plastics For Food, Study Finds

Researchers of a new study found that sea turtles end up eating plastic not just because of how they look but, also because of how they smell. Evidently, sea turtles tend to mistake smelly plastic for food.

'Biofouled' Plastics

Sea turtles have been long thought to consume plastic because they visually mistake them for their usual prey such as jellyfish. However, not a lot is known about the sensory mechanisms that actually lead or attract sea turtles to consume plastic.

Recent findings have suggested that the same airborne odorants that marine predators use to locate prey also emanate from "biofouled" plastic debris or plastics in the ocean that has accumulated algae, microbes, plants and small animals on their surfaces.

Is it possible that these airborne odorants also contribute to sea turtles’ attraction to marine debris?

Sea Turtle Experiment

To find out, the researchers conducted an experiment with 15 captive-reared turtles that were collected from Bald Head Island, North Carolina. The sea turtles were first subjected to a 20-minute air-out period in which residual odors were removed before placing them in the experiment arena.

During the experiment, airborne odorants were delivered through a pipe into the experimental arena and allowed to accumulate for two minutes. Each sea turtle was exposed to four different treatments: deionized water (control), clean plastic (control), turtle food and biofouled plastic.

Interestingly, the sea turtles responded to the biofouled plastic in the same way that they responded to food. In fact, the turtles protruded their nares out of the water over three times longer in response to food and biofouled plastics compared to the control odors.

"We were surprised that turtles responded to odors from biofouled plastic with the same intensity as their food," study co-author Joseph Pfaller said. "We expected them to respond to both to a greater extent than the control treatments, but the turtles know the smell of their food since they've been smelling and eating it in captivity for 5 months. I expected their responses to food to be stronger."

Simply put, it is possible that sea turtles mistake the plastics for food because of the way that they smell.

Olfactory Traps

According to the researchers, their study provides a possible explanation for why sea turtles eat plastics apart from the "plastic-jellyfish" hypothesis, which does not explain why they also eat plastics that don't look like jellyfish at all. That said, further studies are needed to get a clearer view of exactly what chemicals in the plastics attract sea turtles and other marine creatures.

"Airborne odorants provide sensory cues that attract marine predators, like sea turtles, to areas with enhanced foraging opportunities," the researchers wrote in their study. "If biofouled plastic debris provides similar cues, then areas of concentrated plastic debris could become 'olfactory traps' that attract turtles from considerable distances away and cause normally adaptive foraging strategies to become detrimental or even lethal."

This is a problem, not just for sea turtles but, for other marine animals that are significantly affected by the ocean plastic pollution problem that we are facing.