Baleen whales use their nostrils to sniff out food – which could make them susceptible to ingesting plastic, warns a new study. Researchers say Baleens, a grouping that includes blue whales, the largest mammal on Earth, may use their smell to seek out zooplankton, which emit a chemical into the ocean.
But this same chemical is also emitted by plastic, leading scientists to fear they could be susceptible to eating the harmful floating waste. The marine scientists behind the groundbreaking study, published in the journal Biology Letters, say further research is urgently needed to assess how whales find food and could be more at risk from floating plastic.
Baleen whales are a grouping that includes blue, humpback and right whales and feed on huge quantities of zooplankton, such as krill, and fish to maintain their bulk. Their acute ability to accurately locate sufficient zooplankton across the vast ocean has until now continually puzzled scientists and remained a mystery.
However, a team of researchers from the Scottish Association for Marine Science (SAMS) in Oban believe they may finally have uncovered one of the food-finding secrets of the giants of the deep.
An aerial view of a North Atlantic right whale exhaling at the surface.
When zooplankton graze on microscopic, plant-like phytoplankton, they release a chemical called dimethyl sulfide – which we know as the smell of the sea – into the ocean and then the air. The scent from this chemical is already known to attract seabirds to feeding frenzies, and researchers now believe it may also provide a signal of food to baleen whales, too.
They say the whales may be able to smell ‘in stereo’ as they boast two nostrils – unlike dolphins which have a single nostril. The revelations therefore highlight an urgent need for further research into whether the same feeding strategy also encourages whales to ingest plastic debris.
Fouling that grows on plastic floating at sea also emits chemical dimethyl sulfide, which is believed to make whales mistake it for food.
The study’s lead author, Dr Conor Ryan, collaborated with an international team of scientists working in every major ocean and used drone images of 14 different species of baleen whale to measure the spacing between the two nostrils on each blowhole. Their findings show that whales with a preference for eating more zooplankton than fish, such as the North Atlantic right whale, have wider spacings between their nostrils – making them better equipped to sniff out the location of grazing zooplankton.
An aerial view of a North Atlantic right whale feeding just below the water’s surface in Cape Cod Bay, Massachusetts.
Dr Ryan, an Honorary Research Fellow at SAMS, asked: “Whales have massive bodies, but how do they meet that huge demand for calories?
“The methods some use to feed, such as lunge-feeding, are also very energetically expensive, so they need to find high densities of prey to make eating worthwhile.
“Phytoplankton emit a gas as they’re being fed on by zooplankton – ‘the smell of the sea’ as we know it – and it is possible that the whales can detect this, a bit like how some birds are attracted by the smell from freshly cut grass.
“Whales that have their nostrils wider apart are better equipped to smell ‘in stereo’ and could potentially locate feeding opportunities by homing in on the source of a smell.”
Whilst the research team’s findings are not yet definitive proof that whales can smell, it marks the first time the stark correlation between feeding preference and the distance between nostrils has been demonstrated.
Dr Ryan says the discovery is a crucial step in discovering more about how whales find food, as well as how they may be threatened as a result by objects such as plastic debris in their environment.
“If indeed whales do locate food by smelling dimethyl sulfide, there is a heightened risk of them eating plastic, because the fouling that grows on plastic floating at sea smells like plankton,” Dr Ryan added.
“This is why some seabirds cannot resist eating plastic and feeding it to their chicks.
“Understanding whales’ ability to smell could help us figure out why some species are so prone to plastic ingestion.”
Produced in association with SWNS Talker
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