Solving the Krill Paradox: Researchers Find Whales Eat (and Poop) Far More Than Previously Thought

Humpback Whale by Boat

Researchers from Stanford University, UC Santa Cruz and Duke University investigate a humpback whale by boat and drone in the surface waters near the Western Antarctic Peninsula. Credit: Duke University Marine Robotics and Remote Sensing under NOAA permit 14809-03 and ACA permits 2015-011 and 2020-016

Research on whale feeding highlights how the precipitous decline of large marine mammals has negatively impacted the health and productivity of ocean ecosystems.

From 1910 to 1970, humans killed an estimated 1.5 million baleen whales in the frigid water encircling Antarctica. They were hunted for their blubber, baleen – the filtering fringe they have in place of teeth – and meat. One might assume that from the perspective of krill – the tiny shrimp-like creatures the whales feast on – this would be a boon. But new research published on November 3, 2021, in Nature from a collaboration led by Stanford University’s Goldbogen Lab suggests the opposite: that the decline of baleen whales in the Southern Ocean has led to a decline of krill.

This paradoxical result is a sign of just how much the precipitous decline of the large marine mammals has negatively impacted the health and productivity of ocean ecosystems, the researchers say.

“Fifty years after we stopped hunting whales, we’re still learning what impact that had. The system is not the same,” said Matthew Savoca, a postdoctoral scholar in the Goldbogen lab at Stanford’s Hopkins Marine Station and lead author of the paper. “We’re looking into ways of using this information to restore ocean ecosystems and bring whales back. And hopefully, that will have benefits for everything from biodiversity conservation to fisheries yield to carbon storage.”

The researchers came to their troubling conclusion after asking a very fundamental question: How much do whales eat?

Modernizing whale research

Large whales are inherently difficult to study because they can’t be studied in captivity. So, previous estimates of how much whales consume were generally limited to either studies of dead whales or metabolic extrapolations based on much smaller animals.

For this study, the researchers looked at blue, fin, humpback, and minke whales – all whales that feed by gulping a large amount of water and filtering it through their mouths’ fringed baleen plates until only their prey remains. They employed several high-tech tagging devices that attach to whales typically for about five to 20 hours, recording their movements, acceleration, sound and, if light allows, video. Drones, operated by the Duke Marine Robotics and Remote Sensing Laboratory, measured the length of individual, tagged whales, which helps the researchers estimate the size of their gulp. In collaboration with the Environmental Research Division at NOAA and the University of California, Santa Cruz, the researchers also ran an underwater device called an echo sounder – which Savoca likens to “a fancy fish finder” – which uses sound waves at several different frequencies to measure how much prey is around.

Whale Tags

Video and 3D-motion tags that are deployed on large whales with suction cups. Credit: Goldbogen Lab

“All of that put together really gives us this amazing view,” said Shirel Kahane-Rapport, a graduate student in the Goldbogen lab and co-author of the paper. “From each one, you can learn a lot about whales, but the combination takes the research to another level.”

Analysis of the data they captured revealed that whales in the Southern Ocean eat about twice as much krill as previous estimates suggested, and that krill-feeding blue and humpback whales off the coast of California eat two to three times as much as previously thought. Fish feeding humpback whales, however, might eat the previously estimated amount or even less. This range seems to reflect the energy density of the food – whales need to eat more krill to get the same energy as they would from a smaller amount of fish.

“As large baleen whales get bigger, the anatomical machinery that allows them to eat also gets relatively bigger,” said Jeremy Goldbogen, co-director of Hopkins Marine Station and associate professor of biology in the School of Humanities and Sciences, who is senior author of the paper. “They have evolved these systems that allow them to be eating machines. That disproportionately bigger gulp size allows them to take advantage of abundant food, like krill.”

The researchers made their estimates of consumption based on their data about prey density, gulp size, and lunge frequency, as recorded by the tags. Going from hours of data to general estimations – and applying those to whales around the world – required careful calculations.

Baleen Whale Field Measurements

Field measurements informing baleen whale prey consumption and nutrient recycling. Photos taken under NOAA permits 16111, 14809, 23095, and ACA permits 2015-011 and 2020-016. Credit: Alex Boersma

“We came up with a very involved process and we try to do our best to retain as much uncertainty as possible along the way,” said Max Czapanskiy, a graduate student in the Goldbogen lab and co-author of the paper. “No one else has data like this. It’s a huge step forward, but at the same time, it’s a hard system to study and there’s still a lot of uncertainty.”

With these new consumption estimates, the researchers calculated that the early 20th-century abundance of krill in the Southern Ocean had to be about five times what it is now in order to feed the pre-whaling whale population. This implies a complex role for whales in their ecosystems where the decline or recovery of their populations is strongly tied to overall ecosystem productivity and functioning.

“Hopefully work like this can really get people to consider the ecosystem-wide repercussions of human activities because we are still continually affecting their environment,” said Kahane-Rapport.

Mobile processing plants

The Southern Ocean is among the most productive ecosystems on Earth, largely due to the abundance of microscopic algae, called phytoplankton. Phytoplankton are a vital food source for krill, small fish, and crustaceans – which are, in turn, consumed by larger animals, including whales, birds and other fish. But whales also help sustain phytoplankton. Through eating krill and then defecating, whales release iron locked within krill back into the water, making that iron available to phytoplankton, which need it to survive.

“Without phytoplankton, you’re never going to get all the animals and everything that we care so much about,” Czapanskiy said. “When whales were very numerous, they had this incredible role in bolstering the ecosystem.”

“Think of these large whales as mobile krill processing plants,” Savoca added. “Each fin whale or blue whale is the size of a commercial airliner. So, in the first half of the 20th century, before whaling, there were an additional one million of these 737-sized krill processing plants moving around the Southern Ocean eating, pooping, and fertilizing.”

The many twists and turns of these findings demonstrate the potential impact of asking simple questions. By trying to pin down how much whales eat, this work has cast doubt upon what people thought whales needed to survive, and how the activities of whales and humans affect ocean ecosystems.

“Just this idea that if you remove large whales, there’s actually less productivity and potentially less krill and fish is amazing,” said Goldbogen. “It’s a reminder that these ecosystems are complex, highly intricate, and we need to do more to fully understand them.”

Read World’s Largest Whales Eat 3x More Than Previously Thought, Amplifying Their Role As Global Ecosystem Engineers for more on this research.

Reference: “Baleen whale prey consumption based on high-resolution foraging measurements” by Matthew S. Savoca, Max F. Czapanskiy, Shirel R. Kahane-Rapport, William T. Gough, James A. Fahlbusch, K. C. Bierlich, Paolo S. Segre, Jacopo Di Clemente, Gwenith S. Penry, David N. Wiley, John Calambokidis, Douglas P. Nowacek, David W. Johnston, Nicholas D. Pyenson, Ari S. Friedlaender, Elliott L. Hazen and Jeremy A. Goldbogen, 3 November 2021, Nature.
DOI: 10.1038/s41586-021-03991-5

Additional Stanford co-authors of this research include graduate students William Gough and James Fahlbusch; postdoctoral scholar Paolo Segre and Elliott Hazen, adjunct professor at Hopkins Marine Station. Other co-authors are from Cascadia Research Collective, Duke University Marine Lab, Oregon State University, University of Copenhagen in Denmark, University of Southern Denmark, Aarhus University in Denmark, Nelson Mandela University in South Africa, National Oceanic and Atmospheric Administration (NOAA)/Stellwagen Bank National Marine Sanctuary, Smithsonian National Museum of Natural History, the Burke Museum of Natural History and Culture, University of California, Santa Cruz and NOAA Southwest Fisheries Science Center. Goldbogen is also a member of Stanford Bio-X and an affiliate of the Stanford Woods Institute for the Environment.

This research was funded by the National Science Foundation, the Office of Naval Research Young Investigator Program, the Defense University Research Instrumentation Program, the National Geographic Society, the Percy Sladen Memorial Trust, the PADI Foundation, the Society for Marine Mammalogy, Torben og Alice Frimodts Fond, the Volgenau Foundation, the International Fund for Animal Welfare, and MAC3 Impact Philanthropies which is part of the Stanford One Ocean Initiative.

5 Comments on "Solving the Krill Paradox: Researchers Find Whales Eat (and Poop) Far More Than Previously Thought"

  1. It doesn’t matter how much is eaten or pooped. It is all from food derived from photosynthetic algal primary productivity at the bottom of the food chain. Whether eaten or not it will be recycled by the oxygen created. That’s part of the carbon cycle. Very little organic matter ever reaches the bottom, much less preserved below the sediment-water interface. Iron has little permanent effect because of that.

  2. Great to hear! Glad our tax money and universities aren’t focused on minor things, like cancer and the homeless, etc. How many scholarships could you offer (in important fields) instead of finding out ludicrous information like this.

  3. Donald McDonald | November 4, 2021 at 7:46 pm | Reply

    Dump some rusting old cars in the Antarctic region and the ocean will have all the iron it needs and fodder for new coral reef formation and we can get some junkyard land back to use for more McDonalds locations since that’s what humans want, their own bottom feeding locations for the worst quality food in the world. 😉

  4. Babu G. Ranganathan | November 5, 2021 at 7:25 am | Reply

    Babu G. Ranganathan*
    (B.A. Bible/Biology)


    When you divide a cake, the cake never gets bigger. However, when we were just a single cell and that cell kept dividing we got bigger. New material had to come from somewhere. That new material came from food.

    Just as the sequence of various letters and words in human language communicate a message and direct workers to build and assemble something so, too, the sequence of various molecules in our DNA (our genes or genetic code) directed molecules (i.e. various amino acids, the building blocks of proteins) from our mother’s food, that we received in the womb, to become new cells, eventually forming all the tissues and organs of our body. Food isn’t just for energy. It’s also material used by the body to make new cells. After all, when we eat meat or vegetables we’re actually eating cells of animals and plants.

    When you feed a cat your food the cat’s DNA will direct the food molecules to become the cells, tissues, and organs of a cat, but your DNA will turn the same food into human cells, tissues, and organs.

    What we call “genes” are actually segments of the DNA molecule. When you understand how your DNA works, you’ll also understand how egg yolks can turn into chickens. Read my popular Internet article: HOW DID MY DNA MAKE ME? Just google the title to access the article.

    This article will give you a good understanding of how DNA, as well as cloning and genetic engineering. You also learn that so-called “Junk DNA” isn’t junk at all. You will learn why it is not rational to believe that DNA code could have arisen by chance. Science points (not proves, but points) to an intelligent cause for DNA code.

    What about genetic and biological similarities between species? Genetic information, like other forms of information, cannot happen by chance, so it is more logical to believe that genetic and biological similarities between all forms of life are due to a common Designer who designed similar functions for similar purposes. It doesn’t mean all forms of life are biologically related! Only genetic similarities within a natural species proves relationship because it’s only within a natural species that members can interbreed and reproduce.

    Nature cannot build DNA code from scratch. It requires already existing DNA code to direct and bring about more DNA code or a genetic engineer in the laboratory using intelligent design and highly sophisticated technology to bring DNA code into existence from scratch. Furthermore, RNA/DNA and proteins are mutually dependent (one cannot come into existence without the other two) and cannot “survive” or function outside of a complete and living cell. DNA code owes its existence to the first Genetic Engineer – God!

    Protein molecules require that various amino acids come together in a precise sequence, just like the letters in a sentence. If they’re not in the right sequence the protein won’t function. DNA and RNA require for various their various nucleic acids to be in the right sequence.

    Furthermore, there are left-handed and right-handed amino acids and there are left-handed and right-handed nucleic acids. Protein molecules require for all their amino acids to be left-handed only and in the right sequence. DNA and RNA require for all their nucleic acids to be right-handed and in the right sequence. It would take a miracle for DNA, RNA, and proteins to arise by chance!

    Mathematicians have said any event in the universe with odds of 10 to 50th power or greater is impossible! The probability of just an average size protein molecule (with its amino acids in the right sequence) arising by chance is 10 to the 65th power. Even the simplest cell is made up of many millions of various protein molecules along with and DNA/RNA..

    The late great British scientist Sir Frederick Hoyle calculated that the odds of even the simplest cell coming into existence by chance is 10 to the 40,000th power! How large is this? Consider that the total number of atoms in our universe is 10 to the 82nd power.

    Also, so-called “Junk DNA” isn’t junk. Although these “non-coding” segments of DNA don’t code for proteins, they have recently been found to be vital in regulating gene expression (i.e. when, where, and how genes are expressed, so they’re not “junk”). Also, there is evidence that, in certain situations, they can code for proteins through the cell’s use of a complex “read-through” mechanism.

    Visit my latest Internet site: THE SCIENCE SUPPORTING CREATION (This site answers many arguments, both old and new, that have been used by evolutionists to support their theory)

    Author of the popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

    *I have given successful lectures (with question and answer period afterwards) defending creation before evolutionist science faculty and students at various colleges and universities. I’ve been privileged to be recognized in the 24th edition of Marquis “Who’s Who in The East.”

  5. Now you tell me! And I just invited several blue whales over for a buffet tonight. *sigh* Back to the market…

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