Why is plastic sometimes found in the stomachs of whales?

How is it that 30 plastic bags find their way into the stomach of a cetacean? The issue was raised after the discovery of a Cuvier’s beaked whale stranded in Norway last January, whose digestive system was filled with plastic bags and other human-generated refuse. Did the beaked whale deliberately eat the garbage?

Plastic bags mainly affect tooth whales because they eat large prey. When swollen with water, bags can resemble squid, a favourite prey of beaked whales and sperm whales. Cetaceans might therefore be deceived about the nature of their meal, despite their echolocation skills…

Considering that a giant squid can measure over 10 metres long, it is understandable that a 13-metre long fishing net or a 70 cm car part might be discovered in a sperm whale beached on Germany’s North Sea coast   Except that these items do not digest the same way as fish do, and cases of perforation, lesions, blockage or malnutrition have been documented in marine mammals.

Smaller objects can be equally harmful and swallowed at the same time as prey. As early as 2011, Whales Online addressed the issue of plastic in the St. Lawrence. At that time, Catherine Couillard, head of ecotoxicology research at the Maurice Lamontagne Institute (MLI) of Fisheries and Oceans Canada, stated that “Ingestion of plastic can sometimes lead to the animal’s death or progressive wasting with waning health and reproductive problems. Plastic pieces are substrates that increase the risk of attachment and introduction of invasive species that may compete with native species and disrupt the ecosystem.” In other words, in addition to harming animals directly, refuse can also affect them indirectly by modifying the ecosystem via the presence of substances that fauna and flora are not accustomed to.