Baleens - beneficial gluttons of the high seas

Scientists believe the ravenous appetites of baleen whales - Earth's largest creatures - and their prodigious waste - hold clues to the very health and productivity of our oceans.

by Larry Powell

A blue whale (Balaenoptera musculus) defecates. Photo credit-Ryan Lavery (Smithsonian)

Baleens include humpbacks, fins, minkes and blue whales, the latter being the largest creatures ever to live on Earth. The carnivorous marine mammals catch and consume vast amounts of prey. And they recycle ocean nutrients by excreting undigested food in what have been described as "volcano-like" movements.

A minke whale tagged by the research team off the coast of Antarctica in 2019. Credit: Ari Friedlaender under NOAA/NMFS permit 23095.

By attaching tags to the backs of 321 whales from seven baleen species, the researchers now reckon that - before the onset of whaling in the twentieth century - and in the Southern Ocean alone - baleens were, amazingly, consuming more than twice what the world's entire marine fisheries catch today. 

A humpback whale feeds on sand lance in the Stellwagen Bank National Marine Sanctuary. Credit: Elliott Hazen

Yearly, they probably ate 430 million tonnes of Antarctic krill (small crustaceans found in all the world's oceans) before whaling ramped up in the 19 hundreds in the Atlantic, Pacific, and Southern Oceans. That's up to thirty percent of their entire body mass, on average, and, in some areas of the ocean at least, triple the volume previously thought. And, incredibly, it's twice the total biomass of this entire species of krill thought to exist today. 

The scientists hope, if baleen numbers could somehow recover to what they were before that twentieth century whaling, their "nutrient recycling services" could not only help boost ocean productivity but restore ecosystem functions to their previous glory.

According to the Smithsonian Institute, heavily involved in the study, whales both eat and excrete immense amounts of iron. It is an important nutrient which spurs the growth of phytoplankton blooms. If it weren't for the whales, this valuable commodity would sink from near the surface, where the whales live (and where the iron is needed), to the bottom where it would be lost. 

These findings have just been published in the journal, Nature.

If you want to save a whale, first save its food

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