The blue whale is larger than any dinosaur that ever existed on Earth. An adult blue whale can reach lengths of over 30 meters and weigh up to 190 tons. Together with the humpback whale and gray whale, blue whales and their giant relatives belong to the baleen whale family, making them some of the greatest creatures known to science.
Given their size, one might assume that whales are voracious eaters. However, new research reveals that we have underestimated the feeding capacity of whales. New data shows that the amount of food consumed by baleen whales exceeds any previous estimates, potentially being three times greater than figures from earlier studies.
This means that they… defecate more often. According to a report published in the journal Nature recently, this is good news for the ecosystem.
The North Atlantic right whale is one of the whale species on the brink of extinction.
The daily diet of baleen whales consists of large quantities of small fish or crustaceans, including mollusks. The byproducts of their digestion continue to provide essential nutrients for the marine ecosystem.
However, due to our unfamiliarity with whale feeding habits and the difficulty in estimating their food intake given their massive size, science has struggled to accurately determine the amount of food consumed by baleen whales. This has also posed a significant challenge for whale conservation.
“If we want to protect whales and ensure they thrive in today’s ocean environment, knowing how much food they need to survive and reproduce is crucial,” said Matthew Savoca, the author of the new study, in an interview with Inverse.
Previous estimates were inaccurate. Errors arose when researchers calculated based on metabolic models of smaller animals (like dolphins), or data from whales in captivity, or by analyzing the remnants of food found in beached whales.
In contrast, the new study directly monitored baleen whale populations in the Atlantic, Pacific, and Southern Oceans, providing more accurate figures on the amount of mollusks consumed by the whales, alongside the waste produced by these giant biological machines.
Using individual tracking methods and acoustic devices, researchers gathered actual data from 300 whale individuals across 7 species within the baleen whale family. This allowed scientists to determine the daily amount of marine organisms consumed by whales, as well as the nutrients returned to the ocean in the form of feces.
Baleen whales are named for their unique upper jaw structure.
Previous studies indicated that baleen whales consumed less than 5% of their body weight in food each day. However, according to the new research, Savoca’s team found that the daily food intake of baleen whales is three times greater than previously estimated; they consume prey weighing between 5-30% of their body weight.
“In short, if whales eat more than estimated, they will recycle more nutrients [for the ocean] – meaning they defecate more than we think,” Savoca noted. By observing the massive amounts of feces produced by whales, scientists can track how nature balances the marine ecosystem.
Every time a whale defecates, a large amount of nutrients returns to the open sea. Zooplankton absorb these nutrients, helping to maintain the health of the ocean.
Researcher Savoca explained: “These whales are not adding iron – or any other nutrients – into the system; they are merely transforming the nutrients found in their prey and releasing them into the ocean. Theoretically, these nutrients will nourish phytoplankton – the foundational units of all food webs in open oceans.”
Phytoplankton.
New studies show a grim outlook if whale populations continue to decline. Between 1910 and 1970, whaling significantly reduced the number of baleen whales. The consequence: the amount of food consumed by whales dropped sharply, and the marine ecosystem lost effective nutrient production machines. It is estimated that before the 21st century (before 1900), baleen whales in the Southern Ocean consumed 430 million tons of mollusks – twice the number of mollusks that exist today.
“Baleen whales maintain the number of mollusks they consume,” noted Victor Smetacek, another whale expert. “Everything deteriorates when whales disappear from the equation.”
The new research provides unprecedented insights into baleen whales while emphasizing the crucial role of these ocean giants in the marine ecosystem.
Humpback whale.
Currently, the population of some baleen whale species, such as the humpback whale, has significantly increased. However, their counterparts have not been as fortunate. Some studies show that the population of baleen whales in the North Atlantic decreased by 8% during 2020, reaching the lowest level in two decades. The absence of baleen whales means the ocean receives fewer nutrients.
Researcher Savoca hopes that his new study will highlight the critical role of whales in the marine ecosystem, thereby boosting conservation efforts for these giant animals. He emphasizes that conservation actions can stem from simple efforts, such as steering boats away from whale migration routes.
“We are trying to use the new information we have gathered to protect whales and help them recover,” Savoca concluded.
