An estimated nine out of ten seabirds have consumed plastic, and scientists wondering exactly why they consume something that could kill them have found that the answer has been right under their noses the entire time – it’s because of its smell.
As BBC News and the Christian Science Monitor explained, scientists from the University of California-Davis have discovered that marine plastic debris gives off the same odor as seaweed that is rotting – a scent that marine birds have long relied upon to help them find food.
“It’s important to consider the organism’s point of view in questions like this,” Matthew Savoca, lead author of a paper published Wednesday in the journal Science Advances, said in a statement. “Animals usually have a reason for the decisions they make. If we want to truly understand why animals are eating plastic in the ocean, we have to think about how animals find food.”
The odor given off by the plastic is caused by the breakdown of plankton adhering to the plastic debris, Savoca and his colleagues explained. It essentially fools the birds into thinking they have found a meal when what they are actually consuming could result in serious injury or death.
“When you think about an animal doing something that’s ‘stupid,’ it might actually make a lot of sense when you consider that organism’s perspective,” he told the Christian Science Monitor. “They have evolved over tens of millions of years to use this cue to find food and so they’re not making a stupid decision, they’re making an incredibly intelligent and very precise decision.”
Plastic’s odor fools birds into thinking krill are nearby
As part of their experiments, Savoca’s team filled mesh bags with microbeads and placed them into the ocean, according to BBC News. After three weeks in the water, they analyzed the plastic beads for chemical signatures, and while they did not find anything out of the ordinary, they did discover that the beads had acquired a sulfur-like chemical odor.
Specifically, the plastic had started to smell like dimethyl sulfide, a smell that is often associated with decaying seaweed or rotting cabbage, the UK news outlet noted. Since seabirds tend to have a good sense of smell, and associate this odor with food, they detect and mistakenly consume the plastic waste. The discovery could result in new ways to prevent accidental plastic ingestion.
In previous research, study co-author Gabrielle Nevitt, a professor in the UC Davis Department of Neurobiology, Physiology and Behavior, found that the smell of dimethyl sulfide causes some seabirds to forage. That’s because its odor resembles that given off by algae being consumed by krill, small crustaceans which are a favorite meal of many types of seabird.
“This study shows that species that don’t receive lot of attention, like petrels and some species of shearwaters, are likely to be impacted by plastic ingestion,” Nevitt explained. “These species nest in underground burrows, which are hard to study, so they are often overlooked. Yet, based on their foraging strategy, this study shows they’re actually consuming a lot of plastic and are particularly vulnerable to marine debris.”
Image credit: Thinkstock
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