The seas are a place of horrors. Sea serpents, monsters and hybrid creatures populate the waters on historical nautical charts. Homer already wrote about monsters like the six-headed Scylla and the Charybdis, which sucked sailors into the depths or fished from their ships. In the Bible a whale swallows the prophet Jonah, in the fairy tales from the Arabian Nights Sinbad the seafarer lands on an island that turns out to be a giant fish. Scandinavian and Icelandic storytellers, on the other hand, were terrified of an octopus that devours ships – or of a giant creature called “Hafgufa”: This lies still in the water and lures prey with its mouth wide open, according to the Norwegian “Königsspiegel”, for example 1250. When enough fish have swam into the mouth, it snaps shut.
What inspired people to write such stories can hardly be explained scientifically today. But at least this Hafgufa animal could not really have been a mythical creature. Like scientists around the marine archaeologist John McCarthy from Flinders University in Adelaide now in the journal Marine Mammal Science arguepeople may have simply been describing whales catching fish in a peculiar way that modern researchers only rediscovered in 2011.
During “trap feeding” or “tread-water feeding” whales stand vertically in the water just below the surface of the sea and open their mouths. Fish may mistake the mouth for rocks promising protection from seabirds and swim in – or be drawn in by the current created by the whale. The spectacle lasts up to half a minute, then the whale closes its mouth and dives. Scientists have now observed this behavior in humpback and Bryde’s whales off Vancouver Island and in the Gulf of Thailand.
Why the animals eat this way is unclear. Most recently, researchers thought they could use it to respond to ocean pollution and the spread of low-oxygen dead zones at medium depths: If there are only fish on the surface, whales have to go up to eat. But it is also possible that the technology is simply convenient. Humpback whales feed on plankton and small fish; when hunting, they like to plow through schools of fish with their mouths open. Is stationary hunting possibly more effective if the prey fish are more loosely distributed? And have the whales been doing this for a long time, regardless of ocean pollution?
Hafgufa and humpback whale use burped leftovers as bait
According to the researchers working with McCarthy, the feeding technique corresponds at least amazingly exactly to the descriptions of the Hafgufa. The scientists write that the details also fit: In the king’s mirror, the animal attracts prey by belching and spitting out some leftover food as bait. And indeed, humpback whales would spread an odor while eating and leave fish remains behind.
He initially thought these similarities were a coincidence, says marine archaeologist McCarthy, according to a press release from Flinders University. However, according to medievalists, the hafgufa is not described in medieval writings as a sea monster, but as a species of whale. And already in the “Physiologus”, an early Christian natural writing that goes back to the second century AD, there is a similar animal: the “Aspidochelone”, a whale that feeds itself in the same way.
They argue that the fact that the descriptions of these animals have remained so similar over the centuries also suggests that they were based on authentic observations. Only in the 17th and 18th centuries would the descriptions have been misunderstood as legends of mythical sea monsters. At best, they would have been adorned a bit beforehand.
Bryde’s whales in the Gulf of Thailand
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(Video: Surachai Passada, TDMCR
In the legends, the Hafgufa is as big as an island and is often confused with one. In the Icelandic saga of Örvar Oddr from the 13th century, for example, the unknown poet tells of his hero sailing through supposed rocks, which in fact were the open mouth of a hafgufa who waited hours for prey. If the scientists are correct, these exaggerations were simply the inevitable bit of sailor’s yarn.
But if so, why has no one seen this feeding behavior of humpback whales for centuries? The researchers working with McCarthy explain this with the sharp decline in the number of humpback whales: According to genetic analyzes, there were probably more than 200,000 of these animals in the North Atlantic alone in the 16th century. It is currently estimated at only a few tens of thousands, but stocks are recovering. Perhaps the sightings will increase again in the future.