“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.

“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.