On our whale watching tour on Sunday, September 6th, we had the chance to witness a behaviour that is still unclear to researchers and thus extraordinarily special to see.
(Read our diary entry from this tour: elding.is/sunday-6-september-2020)
That afternoon, we watched a group of 3 humpback whales bubble net feeding! This is a behaviour when the whales release a series of bubbles, either in a line or as a spiral, to produce a 'net' of bubbles. These nets are in a cylindrical shape so that the inside, which can be as wide as 30 metres in diameter, is bubble free. Within these nets they can trap and accumulate their prey, as some fish species for still unknown reasons, refuse to swim through such a wall or net of bubbles. And once the fish are all huddled in one ball, the whales will simply swim through this ball from down below, mouth wide open (called 'lunge feeding'), to catch as much of the fish as possible in one time.
Incredible are the findings researchers are still making about this feeding technique. It was not recorded in Icelandic waters until 2016 in Skjálfandi bay! And the techniques seem to vary geographically. For example, humpback whales in Alaska have been witnessed using not only the bubble nets, but adding in the use of their pectoral fins (the fins on the side of their body), to herd the fish even more efficiently. In addition, a so called 'feeding call' has been recorded when such bubble net feeding occurs. One reason could be to give the “go” to the entire group of whales to lunge upwards through their bubble net at a synchronised time. Other theories are that the sound also gets trapped within the bubble net, thus creating a 'wall of sound'.
The ocean and its inhabitants just never seize to fascinate us and we are nowhere near understanding its entirety. It will be exciting to see if this behaviour will be witnessed more in the coming years!
Article by head researcher Sabrina Voswinkel