Blue whale diet reaches 16 tons in one day and is essential for the ecosystem

The voracity of whales is three times greater than previously believed, according to a study published this Wednesday (3), which highlights the essential role of these animals, decimated by hunting, in marine ecosystems.

Humpback whales, blue whales – the largest living animal on the planet – and other species filter seawater through their fins to feed on krill and small prey.

The authors of the study published in the journal Nature followed 321 whales in their eating habits and found that a single blue whale eats about 16 tons of krill per day, although it does not feed every day.

“It is an animal the size of an airplane, which absorbs the volume of a swimming pool in a few seconds”, highlights the author of the study, Mateus Savoca.

“Imagine running three marathons and eating as much as possible and doing it for most of the summer,” he told AFP. “It’s pretty crazy.”

Based on daily estimates of seven species in Antarctica, the study calculates that whale populations consumed up to 430 million tons of krill a year before they were decimated by hunting, double the amount of krill that exists today.

Krill is especially rich in iron. Once digested by whales and released as faeces, it provides an essential nutrient for the rest of the ecosystem, particularly phytoplankton.

This seagrass feeds many organisms in the oceans, provides an important part of the oxygen we breathe and stores carbon.

“The nutrients that phytoplankton need are present in krill and the whales’ intestines allow the release of iron”, describes Matthew Savoca, a researcher at Stanford University in the United States.

This phenomenon could explain the decline in krill populations, which did not thrive when whale populations were decimated.

In the 20th century, around 1.5 million whales were hunted in the Southern Ocean.

“In the case of blue whales, they were more than 99% of the population”, says Mateus Savoca.

The re-establishment of these populations – now threatened by climate change, collisions with ships, fishing and hunting nets that some countries still practice – would allow a virtuous circle to start for the entire marine ecosystem. “Not only would there be more krill, but also more fish and a healthy ecosystem.”