Why do seabirds eat plastic?
Heartbreaking stories of seabirds eating plastic — and the accompanying horrible images— are everywhere, but now scientists are an important question: Why do seabirds eat plastic in the first place? And why are some more likely to have bellies full of plastic than others?
The answer, it turns out, lies in a compound called dimethyl sulfide, or DMS, which emits a “chemical scream” that some birds associate with food. When seabirds find chunks of plastic bobbing in the water, they gobble them up, not realizing that they’ve just consumed something very dangerous.
Researchers at the University of California, Davis took some samples of plastic sewn into mesh bags and let them marinate in the ocean before bringing them to the viticulture lab, of all places — the facility has incredibly sensitive equipment for sniffing out unique chemical signatures.
Researchers found that the plastic reeked — from a bird’s perspective, anyway — of DMS, a compound emitted by algae as it breaks down. Algae commonly emits DMS when it’s being snapped up by krill and other microorganisms that some birds feed on, so the smell is essentially like a dinner bell.
This finding also provided insight into why some birds are more prone to eating plastic than others.
Birds that respond to DMS do so because they have a sensitivity to it, and use this scent to track down food sources. Seabirds that don’t rely on algae-eaters for food will still eat plastic, but in much smaller numbers.
The study could also be helpful for examining plastic consumption in species beyond the bird kingdom, and suggests that other compounds in plastics could send out their own signals to hungry wildlife.
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Photo credit: Duncan