Plastic bags in the ocean can look just like a jellyfish or other gelatinous creature, fooling loggerhead turtles into hunting them.
This case of mistaken identity, documented in the latest issue of the journal PLoS ONE, reveals how our garbage can hurt marine wildlife. Even if a turtle doesn’t ingest the bag, the effort to explore and grab it wastes the turtle’s energy and time.
Tomoko Narazaki and colleagues from the University of Tokyo outfitted the loggerhead turtles with 3D loggers and crittercams, which enabled the scientists to record all of the turtle action as the animals swam in open water.
Narazaki and his team discovered that the turtles rely on sight, rather than on sound or smell, to find and move toward gelatinous prey, such as jellyfish and other organisms. That’s bad news for the turtles, because a plastic bag looks just like a jellyfish when the bags are submerged in water.
That’s hard to imagine, but the bags tend to lose their shape and take on a more tubular form when submerged. As they float downward in the water, the plastic undulates, making the bag look just like a living, moving jellyfish. I’ve seen this before myself, and the resemblance is uncanny.
The discovery also suggests that loggerhead turtles may rely on jellyfish and similarly textured prey for food more than was previously theorized. Because these squishy organisms aren’t exactly jam packed with nutrients, they serve more as a snack for the turtles. But the turtles seem to go after them quite often during their swimming trips, and particularly during oceanic migrations.
Because of their Jello-like texture, such foods are easy for the turtles to digest, not bogging them down when they have to keep moving. At other times, the turtles tend to go after hard-shelled prey, such as mollusks.
Loggerhead turtles are endangered. It’s a shame to see them, and other turtles, having to deal with our trash seemingly every minute of their lives. Watch as this turtle has to swim through all kinds of discarded waste.
We can help by choosing reusable cloth or other natural material bags instead of plastic. Certain cities around the country, such as Berkeley, already have laws in place that help to limit plastic bag use.
Other litter eventually washes into open water areas, home to species already struggling due to human hunting, habitat loss and other human-caused problems.
Image: Loggerhead turtle from the study outfitted with a 3-D logger; Credit: Tomoko Narazaki/Atmosphere and Ocean Research Institute, The University of Tokyo