Scientists think they've figured out why so many seabirds feast on plastic floating in the ocean, often with deadly consequences. It turns out that the plastic smells an awful lot like the small crustaceans known as krill that are a staple of the birds' diet, reports New Scientist. The finding suggests that while the birds' have a sophisticated sense of smell, it hasn't evolved fast enough to stay ahead of the deceptions of plastic, researcher Matthew Savoca of the University of California, Davis, tells the New York Times. The problem is a big one given the growing piles of plastic trash in the ocean and the growing number of birds found dead with plastic in their bellies. Seabirds use both their vision and sense of smell to find prey, an insight that led to the discovery.
"No one’s actually tested the way plastic smells before," says Savoca. To do so, they soaked plastic in seawater for three weeks, placed the samples in airtight vials, and found that, because of algae, the plastic ended up reeking of a particular sulfur compound. It appears to have a strikingly similar scent to the algae-eating krill the birds have eaten for thousands of years, reports the Independent. Sure enough, researchers combed through studies and found that species drawn to that smell eat plastic six times more often than other birds, they report in Science Advances. Also not helping: bright colors. If something "not only looks like food, but it also smells like food, you’re going to be more likely to eat that thing,” says Savoca. (Seabird populations are plummeting.)