Plastic trash sounds just like food to deep-diving whales

A new study has revealed an intriguing phenomenon that could be contributing to the increasing consumption of plastic waste by whales.

It all starts within the mysterious depths of the ocean where sunlight does not venture. This is where the likes of sperm whales and goose-beaked whales forage for food, relying on their intricate soundwave-based navigation system to find their next meal.

But there seems to be a hitch – a torn plastic party balloon can sound remarkably similar to a delicious squid in these lightless depths.

A recent study has found a potential reason why whales might mistake plastic for prey – they sound the same underwater.

Acoustic signatures in the deep sea

What exactly are these acoustic signatures? Well, when a whale sends out clicks and buzzes from a vocal cord-like structure near their blowholes, the sounds bounce off objects in the water.

The sounds that return carry information about the size, shape, and nature of those objects. This is how the whales “see” and interpret their surroundings. And to their acoustic perception, their favorite squid sounds eerily similar to a plastic bag.

“There are hundreds of types of plastic, and the various material properties including polymer (chemical) composition, additives, shape, size, age/weathering, and degree of fouling likely play a role in the frequency-specific responses observed,” noted the study authors.

Plastic pollution and whales

Now, it’s crucial to mention that the whales’ sound-based navigation system is not a new kid on the evolutionary block. This sophisticated system has been helping whales find food in the pitch-dark ocean depths for the past 25 million years.

However, plastic pollution is a relatively new challenge faced by whales, and according to Merrill’s findings, it’s messing with their ultrasonic grocery shopping.

Plastic debris around whales

Merrill and his team collected typical plastic trash items like shopping bags, ropes, bottles, and balloons from beaches in Beaufort and Atlantic Beach, North Carolina.

These items were then suspended underwater and subjected to sonar transponder tests on Duke Marine Lab’s ship, the R/V Shearwater.

The team performed acoustic testing on these items at three varying sonar frequencies that span the range of ‘clicks’ emitted by different species of deep-diving whales.

The sounds of real squid (albeit deceased ones) and pieces of squid beak were also recorded for comparison.

Whales mistake plastic for prey

The results were as alarming as they were surprising. The plastic debris almost always sounded like food, especially plastic films and fragments, which are among the most commonly found items in the stomachs of deceased whales.

Merrill suggests that we could consider re-engineering some plastics to not have an acoustic signature. But he also warns of potential risks.

For instance, if fishing net and fishing line became “acoustically invisible,” that could lead to increased entanglements where whales wouldn’t be able to identify and avoid these threats.

For this pioneering study, Merrill collaborated with scientists from neighboring marine labs operated by NOAA, NC State University, and UNC – Chapel Hill.

Implications for conservation efforts

The findings from Merrill’s study have profound implications for marine conservation strategies aimed at protecting whales.

Traditional approaches have largely focused on reducing the amount of plastic that enters the oceans – a task vital to the health of marine ecosystems.

However, understanding that plastic can acoustically resemble prey to whales suggests that addressing the challenge could require innovative solutions within the manufacturing sector as well.

This could involve developing materials that emit distinct acoustic signatures detectable by marine life without posing any risk of ingestion.

Such multidisciplinary cooperation between conservationists and material scientists could pave the way for groundbreaking strategies to safeguard these majestic creatures.

Addressing the plastic crisis

In light of these revelations, there is an urgent need to collectively address the plastic pollution crisis. Reducing our reliance on harmful plastics and advancing research into safer alternatives is paramount.

Moreover, stringent regulations on plastic manufacturing could play a crucial role in mitigating this crisis. By innovating responsibly and enforcing global standards, we can not only protect marine biodiversity but also ensure a healthier planet.

While technological innovations and alternatives to plastic are critical in addressing this issue of whales, perhaps the more immediate and straightforward action we can all take is responsible disposal of our waste.

The study is published in the journal Marine Pollution Bulletin.

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