Mysterious new behavior seen in whales may be recorded in ancient manuscripts

Feeding strategy recently discovered in whales may explain strange creatures described in Classical and Norse eras.


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Low res fig03 pngAn illustration from the Bern Physiologus labelled De Ceto Magno Aspidohelunes (on this great Aspidochelone) (Bern, Burgerbibliothek  Credit Cod. 318fol. 15v: CC BY 4.0, color and contrast corrected).

Low res fig05 pngOrtelius's 1658 map of Iceland showing various mythological sea creatures. Below, a detail of a sea creature labelled H, ‘the greatest of whales’ which could not chase fish but caught them through cunning (Public Domain, color and contrast corrected).

In 2011, scientists recorded a previously unknown feeding strategy in whales around the world. Now, researchers in Australia think they may have found evidence of this behaviour being described in ancient accounts of sea creatures, recorded more than 2,000 years ago.

They believe that misunderstandings of these descriptions contributed to myths about medieval sea monsters.

Whales are known lunge at their prey when feeding, but recently whales have been spotted at the surface of the water with their jaws open at right angles, waiting for shoals of fish to swim into their mouths. A clip of this strategy was captured in 2021 and went viral on Instagram.

This strategy seems to work for the whales because the fish think they have found a place to shelter from predators, not realising they are swimming into danger.

It’s not known why this strategy has only recently been identified, but scientists speculate that it’s a result of changing environmental conditions - or that whales are being more closely monitored than ever before by drones and other modern technologies.

Dr John McCarthy, a maritime archaeologist in the College of Humanities, Arts and Social Sciences at Flinders University, first noticed intriguing parallels between marine biology and historical literature while reading about Norse sea monsters.

“It struck me that the Norse description of the hafgufa was very similar to the behaviour shown in videos of trap feeding whales, but I thought it was just an interesting coincidence at first. Once I started looking into it in detail and discussing it with colleagues who specialise in medieval literature, we realised that the oldest versions of these myths do not describe sea monsters at all, but are explicit in describing a type of whale, says Dr McCarthy.

“That’s when we started to get really interested. The more we investigated it, the more interesting the connections became and the marine biologists we spoke to found the idea fascinating.

Old Norse manuscripts describing the creature date from the 13th century and name the creature as a ‘hafgufa’.

This creature remained part of Icelandic myths until the 18th century, often included in accounts alongside the more infamous kraken and mermaids.

However, it appears the Norse manuscripts may have drawn on medieval bestiaries, a popular type of text in the medieval period. Bestiaries describe large numbers of real and fantastical animals and often include a description of a creature very similar to the hafgufa, usually named as the ‘aspidochelone’.

Both the hafgufa and aspidochelone are sometimes said to emit a special perfume or scent that helps to draw the fish towards their stationary mouths. Although some whales produce ambergris, which is an ingredient of perfume, this is not true of such rorquals as the humpback.

Instead, researchers suggest this element may have been inspired by the ejection of filtered prey by whales, to help attract more prey into a whale’s mouth.

Research co-author Dr Erin Sebo, an Associate Professor in Medieval Literature and Language in the College of Humanities, Arts and Social Sciences at Flinders University, says this may be another example of accurate knowledge about the natural environment preserved in forms that pre-date modern science.

“It’s exciting because the question of how long whales have used this technique is key to understanding a range of behavioural and even evolutionary questions. Marine biologists had assumed there was no way of recovering this data but, using medieval manuscripts, we’ve been able to answer some of their questions.”

“We found that the more fantastical accounts of this sea monster were relatively recent, dating to the 17th and 18th centuries and there has been a lot of speculation amongst scientists about whether these accounts might have been provoked by natural phenomena, such as optical illusions or under water volcanoes. In fact, the behaviour described in medieval texts, which seemed so unlikely, is simply whale behaviour that we had not observed but medieval and ancient people had.” 

The new paper on ancient descriptions of whales is: McCarthy, J., Sebo, E. and Firth, M., 2023. Parallels for cetacean trap feeding and tread-water feeding in the historical record across two millennia. Marine Mammal Science, pp.1-12. Accessible in full at

The original 2017 description of the tread-water feeding behaviour by whales in the Gulf of Thailand is: Iwata, T., Akamatsu, T., Thongsukdee, S., Cherdsukjai, P., Adulyanukosol, K. and Sato, K., 2017. Tread-water feeding of Bryde’s whales. Current Biology, 27(21), pp.R1154-R1155. 

Marine Mammal Science 10.1111/mms.13009