Plastic pollution wreaks havoc on whales’ echolocation skills

Scientists from Duke University conducted research indicating that whales might mistake plastic debris for their natural food. As specialists point out, plastic reflects sound in a way similar to some organisms that whales feed on.

Their acoustic signatures are similar, which might be why these animals are inclined to eat plastic instead of, or in addition to, their natural food," emphasized Greg Merrill, the lead author of the study, whose results were published in the journal "Marine Pollution Bulletin."

Whales, such as sperm whales, pygmy sperm whales, or beaked whales, use a highly developed sound reception system to find food in the dark ocean depths.

All tested marine plastic debris have similar or stronger acoustic values compared to those of whale prey, researchers noted.

Thanks to their special anatomical structure, whales produce sounds from formations resembling vocal cords, which are located near their nostrils. This acoustic wave is transmitted into the water by the melon, an oil-filled structure located above the head.

The reflected sounds are then detected by receptors located in the lower jaw, and subsequent signals are sent to the inner ear and brain of the animal, allowing it to recognise objects in its environment. This system has been functioning uninterrupted for 25 million years, but the presence of plastic in the oceans disrupts its operation.

Every year, hundreds of thousands of tonnes of plastic waste enter the oceans, polluting the natural environment. While shopping, carrying plastic bags, using rubber balloons, or other consumer products, people do not realise that these objects, once they end up in the seas and oceans, can be mistaken for food by marine mammals.

To determine how plastic debris is perceived by whales, scientists collected waste from a beach in North Carolina and tested its ultrasound reflections using sonar. "These were plastic bags, balloons, things often found in the stomachs of stranded whales," explained Merrill.

For comparison, researchers also tested real squids and fragments of this cephalopod's beak found in the remains of a sperm whale. The results clearly indicated that plastic often exhibited similar acoustic properties to the whales' actual food.

Although one potential solution to the problem would be to redesign plastics to remove distinct acoustic signatures, the authors are unsure if this is feasible.

However, I don't think that's really a viable option, because if fishing nets and lines become invisible, whales will entangle themselves more easily. We don't want them to be unable to recognise them, added Greg Merrill.