Findings in title quoted from the linked^1 and hyperlinked^2 content.

From the linked summary:^1

>In 2011, Bryde’s whales in the Gulf of Thailand were first observed at the surface of the water with their jaws open at right angles, waiting for fish to swim into their mouths.

>Scientists termed the unusual technique, then unknown to modern science, as “tread-water feeding”.

>Around the same time, similar behaviour was spotted in humpback whales off Canada’s Vancouver Island, which researchers called “trap-feeding”.

>In both behaviours the whale positions itself vertically in the water, with only the tip of its snout and jaw protuding from the surface.

>Key to the technique’s success, scientists believe, is that fish instinctively shoal toward the apparent shelter of the whale’s mouths.

>Flinders University scholars now believe they have identified multiple descriptions of the behaviour in ancient texts, the earliest appearing in the Physiologus – the Naturalist – a Greek manuscript compiled in Alexandria around 150-200CE.

> 

>In the Naturalist – a 2,000-year-old text that “preserves zoological information brought to Egypt from India and the Middle East by early natural historians like Herodotus, Ctesias, Aristotle and Plutarch” – the ancient Greeks referred to the creature as aspidochelone.

>Dr John McCarthy, a maritime archaeologist at Flinders University in Adelaide, South Australia, and the study’s lead author, made the discovery while reading Norse mythology, about a year after he had seen a video of a whale tread-water feeding.

>He noted that accounts of a sea creature known as hafgufa seemed to describe the feeding behaviour.

>The most detailed description appeared in a mid-13th-century Old Norse text known as Konungs skuggsjá – the King’s Mirror. It reads:

>>“When it goes to feed … the big fish keeps its mouth open for a time, no more or less wide than a large sound or fjord, and unknowing and unheeding, the fish rush in in their numbers. And when its belly and mouth are full, [the hafgufa] closes its mouth, thus catching and hiding inside it all the prey that had come seeking food.”

>The researchers noted: “Definitive proof for the origins of myths is exceedingly rare and often impossible, but the parallels here are far more striking and persistent than any previous suggestions.”

^1 Ancient texts shed new light on mysterious whale behaviour that ‘captured imagination’, Donna Lu for The Guardian, 28 Feb. 2023, https://www.theguardian.com/environment/2023/mar/01/ancient-texts-power-new-light-shed-on-mysterious-whale-behaviour-that-captured-imagination

^2 McCarthy, J., Sebo, E., and Firth, M. Parallels for cetacean trap feeding and tread-water feeding in the historical record across two millennia. Marine Mammal Science 2023. https://doi.org/10.1111/mms.13009