Why plastic is a deadly attraction for sea turtles
Scientists have additional evidence to explain why plastic is dangerous to sea turtles: the animals mistake the scent of plastic for food. A plastic bag floating in the sea not only looks like a jellyfish, but it also gives off a similar scent.
This "olfactory trap" might help explain why sea turtles are prone to eating and getting entangled in plastic. As plastic debris like bags, netting and bottles is accumulating in our oceans the thread to the sea turtles, birds, whales and hundreds of other marine species is becoming an ever more serious issue. As plastics spent time in the ocean, they develop smells that turtles are attracted to and this is an evolutionary adaptation for finding food.
Once plastic has been released into the ocean, microbes, algae, plants and tiny animals colonize it and make it their home. This creates food-like scents which have been shown to be a magnet for fish and sea birds. The recent research suggests sea turtles are also attracted to plastic for the same reason.
Marine predators like sea turtles, whales and seabirds hunt over a vast area to find food and it makes sense that they would use "chemical detectors" to do so. It is not just a visual thing – they are being attracted from interminable distances away to these garbage patches out in the open ocean.
We well know the danger of items like straws and plastic bags for sea turtles. A section of the video where a plastic straw stuck up a turtle's nose went viral on social media in 2015 can be seen here:
The errant plastic straw in a turtle's nose or the random plastic bag - sure those are absolute problems - but anything out there can grow bacteria and animals on it that turtles want to eat and so it smells to them like something they should go check out and consume, which can lead to their death. The findings, published in Current Biology, are based on an experiment involving 15 young loggerhead sea turtles that had been raised in captivity.
The researchers piped airborne scents into the air above a water tank and recorded the turtles' reactions with cameras. The animals responded in the same way to odors from conditioned plastics released into the air as they did to food such as fish and shrimp meal. When they came up to breathe, they kept their noses out of the water over three times longer than normal to get a good smell of the weathered plastics.
The findings open up new avenues for research to protect the marine animals that are threatened by plastic debris in the sea, through entanglement and ingestion. A recent study found that given current trends, 99% of seabirds will have ingested plastic waste by 2050.