John McCarthy, Flinders University
About 10 years ago, marine biologists witnessed two different species of whales in different geographic locations engaged in a novel feeding strategy. The whales would position themselves on the surface of the water and remain motionless with their mouths open. Fish swam into their mouths, and whales broke their jaws and swallowed. It has been referred to as trap feeding or water feeding. A clip of whales feeding on traps even went viral on Instagram in 2021.
However, this feeding strategy might not be as recent as scientists initially thought. Researchers at Flinders University in Australia have found startling descriptions of what looks a lot like trap feeding in Old Norse descriptions of the behavior of a sea creature called hafgufa, according to a new paper published in the journal Marine Mammal Science. That creature, in turn, can be traced back to medieval bestiaries and to a type of whale called aspidochelonefirst mentioned in an Alexandrian manuscript from the 2nd century CE called the physiologist.
“It’s exciting because the question of how long whales have used this technique is key to understanding a variety of behavioral and even evolutionary questions,” said co-author Erin Sebo, a medievalist at Flinders University. “Marine biologists had assumed there was no way to recover this data but, using medieval manuscripts, we have been able to answer some of their questions.”
Whales display a variety of feeding strategies. For example, ramming feeding involves attacking schools of fish with their mouths open, while bubble-net feeding whales create a round curtain of bubbles to concentrate the fish before charging toward the center to feed. Scientists first observed lobtail feeding in the 1980s, a novel behavior that appears to have been driven by a sharp decline in herring populations due to overfishing. Behavior is culturally transmitted between associated groups of whales.
John McCarthy, Flinders University
Trap feeding was first recorded in 2011 in a group of humpback whales feeding on herring off Vancouver Island. The discovery was published in 2018 after a separate 2017 paper reported similar feeding behavior among Bryde’s whales feeding on anchovies in the Gulf of Thailand. Similar to the emergence of wolftail feeding, some researchers hypothesized that the behavior evolved in response to increased pollution, “dead zones,” algal blooms, and similar environmental challenges, which had led to the whale prey closer to the surface of the water. Others thought it might just be a particularly energy-efficient means of feeding when the fish population is less densely packed.
Co-author John McCarthy, a maritime archaeologist at Flinders University, thought the recent trap-feeding behavior was strikingly similar to Norse descriptions of the hafgufaespecially in a 13th century text called king mirror (Konungs skuggsjá). It is described as a large sea creature with an unusual feeding method:
(When) when he goes to feed, he burps a lot from his throat, along with which a large amount of food comes out. All kinds of fish, small and large, gather in the vicinity, seeking to acquire food and a good livelihood there. But the big fish keeps its mouth open for a while, no more or less wide than a great estuary or fjord, and without knowing it or paying attention, the fish rush in en masse. And when its belly and its mouth are full, (the hafgufa) closes its mouth, trapping and hiding within it all the prey that had come in search of food.
That’s a remarkably accurate description of trap feeding, and key details are also found in earlier medieval bestiaries and those mentioned above. physiologist– A creature that holds its maw open, emitting a scent or scent that attracts small fish to jump into its mouth, with the creature closing its maw and swallowing when enough fish have accumulated in the trap. “The tradition remained remarkably coherent and constant for 1,500 years, with minimal embellishment or reinterpretation,” the authors wrote. Also, the creatures in those earlier source texts are identified as whales, not mythical sea monsters. Many of those texts also have illustrations showing sea creatures consuming fish in a way reminiscent of trap feeding.