Filthy plastic floating through the ocean is killing sea turtles, and now researchers think they may be closer to understanding why.
Previously, it was thought the turtles were attracted to plastic waste because they mistook it for prey, confusing things like plastic bags for jellyfish.
But new research from the US, released today, suggests there may be a different reason for it.
As the plastic spends time in the ocean, microbes, algae, plants and small animals accumulate on its surface.
Instead of just visually mistaking it for prey, the researchers think that smell of the plastic is also tricking the turtles.
"We found that loggerhead sea turtles respond to odors from biofouled plastics in the same way they respond to food odorants, suggesting that turtles may be attracted to plastic debris not only by the way it looks, but by the way it smells," says researcher Joseph Pfaller from the University of Florida.
"This 'olfactory trap' might help explain why sea turtles ingest and become entangled in plastic so frequently."
Fifteen young, captive-reared loggerhead turtles were used in the research.
Different scents were pumped into the testing area and the researchers found the turtles would react to the smell of their food in the same way as the fouled plastic, lifting their heads out of the water and sniffing the air for longer than the control odors.
Mr Pfaller says they were surprised by the results, expecting the turtles to react more to their food - which they're used to - than the biofouled plastic.
"The plastic problem in the ocean is more complex than plastic bags that look like jellyfish or the errant straw stuck in a turtle's nose," he says.
"These are important and troubling pieces to the puzzle, and all plastics pose dangers to turtles."
More studies are needed to help figure out what it is about the plastics that's making them so alluring for turtles, Mr Pfaller says, such as which chemicals are coming from the plastic.
The research was published in the journal Current Biology today.