There's a Stinky Reason Seabirds Eat Plastic


A juvenile Andean gull takes a plastic tub in its bill. A new study explains why birds eat so much plastic. Rick Price/Getty Images
A juvenile Andean gull takes a plastic tub in its bill. A new study explains why birds eat so much plastic. Rick Price/Getty Images

It's not quite the notes of blackberry with oaky overtones, but marine scientists recently called on wine chemists to help determine why plastic smells like food to seabirds. The chemists found out the plastic left in the ocean has a hint of the sulfur compound dimethyl sulfide, or DMS, a chemical released by algae. And even though it's stinky (DMS' odor has been likened to rotten cabbages),  that smell is like a dinner bell for some long-billed, super-sniffer seabirds.

The study, published in Science Advances, examined why some seabirds mistake plastic for chow. It turns out DMS is a smell they associate with the aroma of food.  Once they realize they've not found food at all, it's too late. They've got a snootful – and a belly full – of plastic. The study also explains why some species – such as petrels, albatross and other tubenoses – are more prone to binging on plastic than others.

"Animals usually have a reason for the decisions they make," says lead author Matthew Savoca, who performed the study as a graduate student at UC Davis, in a press release. "If we want to truly understand why animals are eating plastic in the ocean, we have to think about how animals find food."

Tubenoses had already been shown to follow their noses to food. So, the first step for this study was to learn what plastic smells like after it's been in the water.  The scientists loaded pellets of three common types of plastic – high-density polyethylene, low-density polyethylene and polypropylene – into mesh bags and tied the bags to a buoy in the ocean at Monterey Bay and Bodega Bay, off the California coast.

Three weeks later, the bags were collected and the wine experts at the UC Davis Robert Mondavi Institute for Wine and Food Science, were called in. A chemical analyzer showed that the plastic smelled of DMS, thanks to algae, which had coated the plastic. The scent is released when animals such as krill, a tubenose favorite, eat the algae. This works to alert the birds to the presence of a meal of their own.

It's a case of having a world-class sniffer not being a good thing. The researchers found that the seabirds that follow their noses via DMS to food are almost six times more likely to ingest plastic as other birds.

A 2015 study estimated that an alarming 90 percent of seabirds eat plastic. Sharp pieces of plastic can injure their internal organs, while soft pieces can affect body weight since the plastic takes up space in the stomach without giving any nutrition. The health effects of plastic on birds have not been completely studied.

In the meantime, give the birds a break, people. Recycle!