Whales More Important for Ecosystem Health Than Previously Thought

Helping them recover could help the marine ecosystem.

Breaching humpback whale megaptera novaeangliae coming out of the water
Tim Melling / Getty Images

The baleen whale buffet table is bigger than researchers thought.

A new study finds that gigantic whales—such as blue, fin, and humpback whales—eat an average of three times more food every year than scientists previously estimated. Since whales ingest more than previously believed, it also means they poop more.

By underestimating how much these massive mammals take in and spew out, scientists may not have fully realized how important these whales are to ocean ecosystem health.

“It's a remarkable fact that we live alongside the largest vertebrates to have lived on the planet—the largest baleen whales are heavier than the largest dinosaurs. We're living in a time of giants, and we hardly know them!” study co-author Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History, tells Treehugger.

“We don't know the answers to the most basic questions of how much they eat, where they move, and how they reproduce. We used real world data on baleen whale feeding and excretion to estimate the amount of food that baleen whales would have eaten prior to 20th century whaling.”

Researchers believe that past estimates about how much whales consume were mostly just guesses.

“Previous estimates were sheer guesses from the prey yields in stomach contents (i.e., the last meal of a hunted whale) or extrapolations from smaller marine mammals, which are poor analogs,” Pyenson says.

Tracking Whales in Real TIme

So for this research, they used data from 321 tagged whales of seven species living in the Atlantic, Pacific, and Southern oceans. The information was collected between 2010 and 2019.

Each tag is attached to a whale’s back via a suction cup and contains a GPS, camera, microphone, and an accelerometer to track movement. The information lets researchers uncover patterns to determine how often the whales were feeding.

They also analyzed 105 drone photographs of whales from all seven species in order to measure their lengths. This information was then used to calculate body mass estimates, as well as the volume of water filtered with each mouthful.

Scientists on the research team also went to sites where whales were feeding. They hurried there in boats with echo-sounders that use sound waves to measure the size and density of the krill and other species the whales are eating. This helped with the estimates of how much food the whales were actually eating.

“These three lines of data were all used to calculate daily consumption for each species of whale using real world numbers,” Pyenson says.

“Our study is the result of many years spent collecting data off boats around the world—answering our questions required building an international collaboration, and coordinating a massive amount of data from different sources, which is all to say that this kind of research is a form of science diplomacy.” 

The results were published in the journal Nature.

Ecosystem Engineers

To put things into perspective, a 2008 study estimated that all the whales in the California Current ecosystem in the northeastern Pacific Ocean, need about 2 million metric tons of fish, krill, and other food each year. The new study suggests that the blue, fin, and humpback whales living in that same area each require more than 2 million tons of food each year.

The study found that an adult eastern North Pacific blue whale likely eats 16 metric tons of krill daily during foraging season, while a bowhead whale eats about 6 metric tons of zooplankton per day, and a North Atlantic right whale eats roughly 5 metric tons of zooplankton daily.

And with so much food coming in, whales also expel large amounts of excrement. Because whales need air to breathe, they tend to poop near the surface of the water. The nutrients in their poop stay close to the water’s surface where they can power phytoplankton. These microscopic plants absorb heat-trapping carbon dioxide, which is notorious for warming the planet. They also play a key role in the marine food web.

“Our results illuminate something that scientists had suspected for the largest whales, but hadn't yet carefully quantified: the scale of their role as ecosystem engineers,” Pyenson says. “If we promote the recovery of these giants, we think that would be a good thing for the health and function of the world's oceans—and good for our own descendants too!” 

The researchers were curious what the ecosystem might have been like before 2-3 million whales were killed due to industrial whaling in the 20th century. They used estimates of how many whales used to live in the region along with their new results to estimate what those animals would’ve eaten.

They calculated that minke, humpback, fin, and blue whales in the Southern Ocean would have eaten about 430 million metric tons of krill each year at the start of the 1900s. That’s double the amount of krill in the entire ocean today and more than double the catch from all wild-capture fisheries combined. They also determined that whale populations pre-whaling produced 10 times the iron in their excrement that they currently make today.

Their findings suggest that when there were so many more whales, there was also likely a lot more krill for them to eat.

“Our calculations suggest that before baleen whales were reduced in dramatic numbers by whaling, they consumed more food than all of the world's krill biomass and global fisheries combined,” Pyenson says.

“The implication of these numbers is that whales supported far more productive ocean ecosystems before whaling, and that promoting whale recovery in the 21st century may restore ecosystem functions lost in the past hundred years.”

View Article Sources
  1. Savoca, Matthew S., et al. "Baleen Whale Prey Consumption Based on High-Resolution Foraging Measurements." Nature, vol. 599, no. 7883, 2021, pp. 85-90., doi:10.1038/s41586-021-03991-5

  2. study co-author Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History

  3. "World's Largest Whales Eat More Than Previously Thought, Amplifying Their Role as Global Ecosystem Engineers." Smithsonian, 2021.

  4. Barlow, J, et al. "Cetacean Biomass, Prey Consumption, and Primary Production Requirements in the California Current Ecosystem." Marine Ecology Progress Series, vol. 371, 2008, pp. 285-295., doi:10.3354/meps07695

  5. "What Are Plankton?" National Oceanic and Atmospheric administration.