Plastic doesn’t just look like food, it smells, feels and even sounds like food.
In a recent interview about Blue Planet II, David Attenborough describes a sequence in which an albatross arrives at its nest to feed its young.
“And what comes out of the mouth?” he says. “Not fish, and not squid – which is what they mostly eat. Plastic.”
It is, as Attenborough says, heartbreaking. It’s also strange. Albatrosses forage over thousands of kilometres in search of their preferred prey, which they pluck from the water with ease. How can such capable birds be so easily fooled, and come back from their long voyages with nothing but a mouthful of plastic?
It’s small comfort to discover that albatrosses are not alone. At least 180 species of marine animalshave been documented consuming plastic, from tiny plankton to gigantic whales. Plastic has been found inside the guts of a third of UK-caught fish, including species that we regularly consume as food. It has also been found in other mealtime favourites like mussels and lobsters. In short, animals of all shapes and sizes are eating plastic, and with 12.7 million tons of the stuff entering the oceans every year, there’s plenty to go around.
The prevalence of plastic consumption is partly a consequence of this sheer quantity. In zooplankton, for example, it corresponds with the concentration of tiny plastic particles in the water because their feeding appendages are designed to handle particles of a certain size. “If the particle falls into this size range it must be food,” says Moira Galbraith, a plankton ecologist at the Institute of Ocean Sciences, Canada.
Like zooplankton, the tentacled, cylindrical creatures known as sea cucumbers don’t seem too fussy about what they eat as they crawl around the ocean beds, scooping sediment into their mouths to extract edible matter. However, one analysis suggested that these bottom-dwellers can consume up to 138 times as much plastic as would be expected, given its distribution in the sediment.
For sea cucumbers, plastic particles may simply be larger and easier to grab with their feeding tentacles than more conventional food items, but in other species there are indications that plastic consumption is more than just a passive process. Many animals appear to be choosing this diet. To understand why animals find plastic so appealing, we need to appreciate how they perceive the world.
“Animals have very different sensory, perceptive abilities to us. In some cases they’re better and in some cases they’re worse, but in all cases they’re different,” says Matthew Savoca at the NOAA Southwest Fisheries Science Center in Monterey, California.
One explanation is that animals simply mistake plastic for familiar food items – plastic pellets, for example, are thought to resemble tasty fish eggs. But as humans we are biased by our own senses. To appreciate animals’ love of plastic, scientists must try to view the world as they do.