Why do seabirds fill their bellies with plastic?

A new study in California suggests that it's all because of the smell emitted by marine plastic debris, which has been found to mirror the "appetizing" aroma of typical seabird meals.

Certain seabirds are normally attracted to the sulfurous stench of dying algae, which, for hundreds of years, has helped them detect where their next feast awaits, scientists said.

Seabirds' Exceptional Sense Of Smell

Up until the middle of the 20th century, scientists never thought that birds could smell at all. But it turns out, tube-nosed seabirds such as kiwis, albatross and petrels use their keen sense of smell to hunt for food.

Their exceptional olfactory sense helps them forage over hundreds or thousands of square kilometers. Unfortunately, petrels, kiwis and albatross are also among species most affected by plastic consumption.

Indeed, because of this olfactory cue, seabirds often make the mistake of chowing down on plastic in increasing quantities, the new study explained.

Hunting For Food

Lead author Matthew Savoca, who conducted the research while he was a graduate student at University of California Davis, believes it is important to consider the animals' point of view in order to understand the reason behind their habits.

To find out why seabirds eat plastic and at the same time, determine what marine plastic debris smells like, Savoca and his colleagues put beads made up of the three most common types of plastic trash into the ocean at Bodega Bay and Monterey Bay.

Researchers were careful enough not to add to the marine plastic problem, so they inserted the beads inside sewn mesh bags, tied them to buoy and then collected them after three weeks. The beads were made up of poly-propylene, low-density polyethylene and high-density polyethylene.

With the help of a special chemical analyzer, scientists confirmed that marine plastic trash did reek of dimethyl sulfide (DMS), a sulfur compound that is released by algae, which coats floating plastic.

Savoca said their findings do not refute that plastic might also look like food to other marine animals that eat it, but it does affirm that when plastic looks and smells like food, it becomes more appealing to seabirds.

"The way the plastic appears visually, from the organism's perspective ... is important to consider," added Savoca.

Experts believe the findings of the study can help in finding new strategies to address the marine plastic problem, which affects not only seabirds, but also sea turtles, fish and other marine life. Meanwhile, details of the new report are published in the journal Science Advances.

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