White plastic appears to pose a particular hazard for penguins, new research from the University of Auckland has found.
University of Auckland research fellow Dr Ariel-Micaiah Heswall tested plastic colour preferences of king and gentoo penguins at Kelly Tarlton’s Sealife Aquarium in Auckland.
She found the 46 gentoo and 23 king penguins interacted far more often with white plastic than other colours, possibly because white reminds them of prey, eggshell or their own feathers.
Penguins are known to eat plastic bottlecaps, so red, blue, black and white caps were used in the experiment.
The seabirds chose white almost twice as often as black, and about 45 percent more often than red or blue.
White plastic could be a “sensory trap” for penguins, because it might lure them with a colour that appeals to their senses, but has harmful consequences when they eat it, says Heswall, from the University’s Faculty of Science and Centre for Climate, Biodiversity and Society – Ngā Ara Whetū.
Previous studies have found more white and clear plastics than other colours in the guts of seabirds in New Zealand and internationally.
Some scientists have suggested that’s because white and clear plastics make up the bulk of the millions of tonnes of plastic floating in the ocean.
However, Heswall’s new research shows penguins select white plastic, even when it’s not more plentiful than other colours.
A study she published in June last year showed white and clear plastics were most often found in the guts of 13 species of North Island seabirds.
Yellow and gold plastics were the next most commonly found inside the seabirds.
While red and green plastics were widespread on Auckland beaches, they were less often found in the seabirds’ guts.
Plastic was found inside all 19 of the Buller’s shearwaters they examined.
“It’s a big problem, but at least we’re beginning to understand it better,” says Heswall.
Putting a lid on the production of white and clear plastics could reduce the threat for many seabird species, she says.
The penguins showed least interest in the black bottlecaps and seldom pecked the blue ones.
“Generally, black plastic is least often found inside most species of seabirds internationally.
“There needs to be more research, but if manufacturers replaced white plastics with black, that could potentially make a big difference for seabirds,” Heswall says.
Globally, 28 percent of seabirds are classified as threatened and seven percent are critically endangered.
Eating plastic poses risks of starvation, as plastic can fill or obstruct the birds’ gut.
Sharp plastics can puncture the gut, but soft plastics, such as balloons, are more likely to result in immediate death for seabirds, Heswall says.
Microplastics can leach into seabirds’ blood streams, changing hormone balances and sometimes causing plasticosis, a disease marked by chronic inflammation and scarring in the digestive tract.
Heswall says the penguin experiments were carefully designed to avoid stressing the birds or posing a risk of plastic being swallowed.
Even though the penguins were free to move around the enclosure, some chose to interact with the plastic caps in all but three of the 41 trials.
Two or three times, the penguins responded to the bottlecaps with courting or reproductive behaviours, flapping their wings and bowing repeatedly.
“It was quite funny to watch.
“The penguins sometimes tried to rotate and turn a bottlecap, a behaviour they typically only display with their eggs.”
Having grown up in Brunei, Heswall only discovered the wonders of seabirds when she moved to New Zealand ten years ago.
“I had no idea of the diverse world of shearwaters and petrels, let alone that New Zealand was the seabird capital of the world.
“I fell in love with seabirds during my university studies,” says the 28-year-old.
