The creatures are fooled by narrow lengths of plastic in natural colours like green and black, such as bin bags, because they look like seagrass, scientists found.
All of the turtles whose full gastrointestinal tract could be examined were found to have swallowed plastic, with 183 pieces found in one animal.
“Previous research has suggested leatherback turtles eat plastic that resembles their jellyfish prey, and we wanted to know whether a similar thing might be happening with green turtles,” Dr Emily Duncan, from the University of Exeter, said.
She added: “Sea turtles are primarily visual predators – able to choose foods by size and shape – and in this study we found strong evidence that green turtles favour plastic of certain sizes, shapes and colours. The sources of this plastic might include things like black bin bags, and fragments from items such as fishing rope and carrier bags.”
Ms Duncan said the research, published in the journal Scientific Reports, suggested turtles favour threads and sheets that are black, clear or green.
However, the team could not determine what role the plastic may have played in the animals’ deaths – although they believed the majority of the 34 turtles examined had most likely died as a result of getting tangled in fishing nets.
The full gastrointestinal tracts of 19 turtles were examined, with the number of pieces found ranging from three to 183.
“Research like this helps us understand what sea turtles are eating, and whether certain kinds of plastic are being ingested more than others,” Professor Brendan Godley, who leads the Exeter Marine research strategy, said.
He added that it was important to know what kinds of plastics were particularly problematic to sea turtles.
The research was supported by Plymouth Marine Laboratory, with funders including the Sea Life Trust and the European Union.
Agencies contributed to this report
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