Why marine animals can't stop eating plastic
Plastic doesn't just look like food, it smells, feels and even sounds like food.
In an 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
animals have been documented consuming plastic, from tiny plankton to gigantic whales. Plastic has
been found inside the guts of a third of UK-caught fish, as reported by Science Direct, and this
includes 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 piece of analysis published by Science Direct
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.