Deep-Sea Danger

The ocean is full of amazing creatures. It’s also full of plastic. There are about 171 trillion pieces of plastic floating in the sea, according to a study published in the journal PLOS One in 2023. That’s bad news for marine animals, such as deep-diving whales. They can mistake the plastic for food and eat it.

How do whales mix up plastic and prey? A team at the Duke University Marine Lab, in Beaufort, North Carolina, has been looking into this question. The team has just published research that explains why some deep-diving whales get confused. It all comes down to echolocation: a natural process that allows whales to “hear” objects in the darkest depths of the sea.

Hunting by Sound, not Sight

Some types of whales, including sperm whales and beaked whales, hunt in the deepest parts of the ocean. There’s little light at those depths, so it’s too dark for the whales to see. But they can hear. To navigate their surroundings, deep-diving whales use sounds produced by echolocation.

OCEAN EXPLORER Sperm whales dive thousands of feet to hunt, deeper than any other marine mammal.

First, the whales make a sound, and then they listen. They hear echoes bouncing off of nearby objects. These echoes allow the whales to hunt. The echoes bounce off of prey animals, like squid, and they bounce off of objects that are not edible, like garbage. The scientists found that garbage and prey cause similar echoes. To the whales, they “sound” the same. That can trick the whales into eating trash.

IT’S A HAZARD Tangled fishing net drifts in the ocean. Whales can mistake it for food. Old nets also trap smaller marine animals.

The scientists gathered items such as bottles, bags, and rope. All of these have been found in the stomachs of whales. The team bounced sounds off of these objects at frequencies × frequency a measure of sound (noun) similar to those that echolocating whales use. A machine measured the strength of each echo. The team then compared these echoes to those produced off the bodies of prey animals. The echoes from the plastic items were similar in strength to those returned by prey animals.

DIVING BUDDIES Two sperm whales dive into the ocean depths. These whales often travel in groups.

Greg Merrill, a marine biologist, is the lead author on the study. He was “kind of unsurprised” by the results. “We knew they were eating [the garbage],” he told TFK. “There had to be a reason.”

Finding a Solution

Eating garbage is dangerous for whales. The plastic can build up in their stomachs, preventing food from passing through their bodies. This can be deadly. “Plastic pollution impacts animals that are so far away from our daily lives,” Merrill says. “This problem is really big.”

WHALE-SIZE PROBLEM This rope protects a coral reef in the Red Sea. Rope is often found in whale stomachs.

Everyone can play a part in reducing plastic pollution. “People need to make real changes in their daily lives, and then advocate for the types of solutions that we need to address this issue,” Merrill says. Advocacy can be as simple as writing to your mayor or governor, he says, or asking your school leaders if they could “make decisions that are more sustainable × sustainable done so as not to cause permanent damage (adjective) .”

Many kids are passionate about marine life. Freddie Slater-Reynolds, 7, is one of them. The study makes him feel “worried” about whales. He shared his advice for people who want to keep trash away from wildlife: Don’t litter. “Throw it in the garbage bin,” he says.

Above and Below

Beaked whales and sperm whales are deep-sea hunters. They dive thousands of feet to find food. But not all whales use echolocation to hunt. Some stick closer to the surface. The humpback whale, like those pictured here, sometimes uses a technique called lunge feeding. The whale opens its mouth wide and surges through a school of fish or krill. If you’re lucky enough to witness a whale’s vertical lunge, you’ll see the huge animal’s head rise above the surface.