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Last blue whales pooping for the planet

Whale manure feeds the gardens of the deep

When it comes to saving the whales, it could be as simple as iron levels.

Scientists onboard the CSIRO’s Marine National Facility’s RV Investigator are now cruising the Southern Ocean in a bid to uncover whether blue whales are basically farming krill on an industrial scale.

Actually, it’s a little more complicated than that - essentially the researchers are endeavouring to discover whether whales are fertilising the waters around large krill swarms with their own poo. It’s the maritime equivalent of spreading manure on your home garden during the spring but in this case, rather than ensuring you grow a bumper crop of summer vegetables, the whales could be assisting in ensuring species survival.

What the scientists hope to understand is whether swarms of krill – the blue whales’ main diet - affect the distribution and behaviour of whales, as well as the interconnection between blue whale poo and krill reproduction in the cold waters of the Southern Ocean.

Australian Antarctic Division marine mammal scientists Dr Elanor Bell and Dr Mike Double are spearheading the effort, which is aimed at maintaining or increasing the numbers blue whales – who are now down to as low as 10,000 today.

The expedition is currently hugging the Antarctic coast, surveying the distribution and behaviour of blue whales in the Ross Sea. Using underwater listening devices originally designed to track submarines in wartime, the crew have found and recorded Antarctic and pygmy blue whales as well as fin, sei, humpback, Antarctic minke, sperm, killer, and pilot whales.

Krill, the primary food source of blue whales.
PHOTO COURTESY OF MIKE JOHNSON

In addition to the vital trace element iron, whale poo also abounds with other nutrients, including dissolved organic carbon, which can stimulate bacterial growth.

But little is known about how these different swarm types of krill are distributed across the Southern Ocean and whether some are more attractive to whales than others.

“Previous research suggests that large, dense swarms may be targeted by fast-moving blue and fin whales that engulf their food, while smaller, deeper krill swarms may be suited to more maneuverable whales, like humpbacks and minkes,” Dr Double said.

IMAGE CREDIT: AUSTRALIAN ANTARCTIC DIVISION

“Understanding which swarms are favoured by which whales will inform the development of ecosystem management tools for whales and the expanding krill fishery.”

Dr Bell said: “We’ll track Antarctic blue whales in real time, from hundreds of kilometres away, using passive acoustic technology that detects their low-frequency calls.”

“Once we find whales we’ll study their distribution and behaviour in the presence and absence of krill. We’ll also look at the characteristics of krill swarms in the presence and absence of whales.”

Don't miss the Australian Museum's Whales | Tohora Exhibition - come face to face with the world's largest animals, the giants of the ocean.

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