Whales in a World of Plastic: Navigational Chaos

BEAUFORT, N.C. -- Scientists conducting a recent study have discovered that deep-diving whales, which rely on echolocation to identify prey in the dark, mysterious waters of the ocean, may be mistakenly ingesting plastic as food. While scientists were able to lead deep-diving whales into traps for a recent study, they may not even be catching the target of the whale's dolphin-like echolocation skills, but, instead, plastic trash. According to researchers from Duke University, the acoustics of plastic waste bear striking similarities to those of squid, which are a primary food source for many whale species. Published in Marine Pollution Bulletin, the study tested various kinds of plastic commonly seen on beaches and in the ocean. They discovered that torn balloons, shopping bags, and other pieces of debris have acoustic signatures very similar to that of whale prey, thereby making it hard for the animals to differentiate. How Whales Hunt in the Deep Whales like sperm whales, pygmy sperm whales, and goose-beaked whales are known to hunt using sound waves. Using a vocal cord-like structure near their blowholes, these deep-diving whales emit clicks and buzzes. These sounds are then emitted through the melon, which is a bulbous oil-filled structure located on the head of the whale, focusing and sending these sound waves into the water around it. When the sound waves strike the object, it bounces back to the whale's jaw, where it gets captured by fat-filled organs. Then the returning echo gets processed by the whale's brain to recognize possible prey. It is a very developed echo-location system, accomplished over millions of years of evolution, with which whales are able to locate food in ocean depths without light. But these systems are increasingly disrupted by the plastic debris that is now found in marine environments. Plastic Debris Mistaken for Food Plastic in the oceans is one of the global concerns because millions of tons of plastic enter this marine environment every year, staying there for hundreds of years. Because of this, plastic often finds its way into the stomachs of whales and other marine animals. The Duke University study was conducted to give an explanation on why whales ingest plastic by examining the behavior of these plastics underwater. Researchers have taken plastic debris from beaches of North Carolina, Beaufort and Atlantic Beach. They used some common plastic objects, including plastic bags and balloons that sometimes get entangled with stranded whales, in the acoustic signature test. The materials were immersed in the ocean and tested using frequencies of sonar which can match clicks produced by deep-diving whales. The plastic objects produced uniformly similar soundwaves with those made by some of the primary prey species of most whale types, namely, squid. This is especially true in regards to plastic films and fragments, the very items commonly found in the guts of stranded whales, which produced strong acoustic signals similar to those made by prey. They also tested actual squid and pieces of squid beak from a dead sperm whale's stomach. These natural food items were used as a benchmark against which the plastic debris could be compared. As results indicate, plastic, especially lightweight and flexible, can easily be mistaken by whales as food due to their echolocation capability. Role of the composition and age of plastic The acoustic signatures of plastic debris thus depend on their composition, size, and condition. Tested materials were a mix of fresh and weathered plastics, including barnacle-coated items collected along the local beaches. It was found that weathering and biofouling of debris had minor changes on how sonar frequencies interacted with these pieces of debris. "There are hundreds of types of plastic," the researchers noted in their report, with varying material properties contributing to differences in acoustic signatures. These factors include chemical composition, size and shape of items, and the level of fouling—the extent to which marine life has attached to the plastic. A Growing Problem for Marine Life Marine pollution, especially plastic debris, has been one of the biggest issues that conservationists and marine biologists face today. Ocean plastics not only kill marine animals through ingestion but also cause entanglement that may cause injuries or death. Mostly, whales and many of the other marine creatures come into contact with those discarded fishing nets and ropes, getting themselves so trapped that they can neither move nor feed anymore. The basis of the growing worries about plastic in the ocean is the results of the research. The acoustic property of plastics makes it hard to avoid that which can be swallowed by the whales, which poses very serious health risks. Plastics may occlude the digestive systems of whales and lead to starvation or death. Solutions and Challenges Such a fundamental problem, finding a solution for is not easy. This is no simple proposition to redesign the plastics with acoustic properties or the kind of property that will contradict the property of echolocation that whales count on when trying to gather food. This, however, poses its own problems. Plastics "made invisible" to echolocation may become increasingly difficult for marine animals to detect dangerous items already causing entanglement problems like fishing nets. Ocean plastics require multiple approaches including stopping the production of plastics, managing waste, and international cooperation to clean up marine environments. Conclusion The study emphasizes the urgent need for dealing with ocean plastics pollution. Along with every increase in the quantity of plastic waste, the risk posed to marine life is also on the increase. In fact, whales use sound for navigation and hunting in the dark depths of the ocean. It makes them one of the most prone species to mistaking plastic debris for food. Diminishing plastic waste and the ways it impacts marine life will play a critical role for health in oceans and their living inhabitants. Source: Study published in Marine Pollution Bulletin and research through Duke University.