Hanging off the side of the rib, I turn my eyes towards the surface of the water. The Arctic summer is here in full force and around us, the fjord hums with life. It’s an unusually warm morning for East Greenland and, at odds with the cacophony of creaking ice and a sky peppered with guillemots and fulmars, the ocean is eerily still. Or at least it was until the bubbles appeared. The bubbles rise faster, one after the other, until at the surface, punctuated by a perfect spiral. Then, with a roar of a blow, a humpback whale rips through the surface tension, letting out a breath of fine mist, which dissipates into the air. The moment is a collision of choreography and power, and demonstrates a behaviour that is now taking place in areas of the Arctic not seen before – the unmistakable sign of humpback whales bubble-net feeding.

Few behaviours speak to humpback whales’ ingenuity quite like that of bubble-net feeding. Scientists consider this to be a form of ‘tool’ using behaviour which demonstrates high social intelligence. This type of foraging is learned, and though it can be seen in populations around the world, not all humpback whales know how to do it. Bubble-net feeding begins underwater, with a whale diving beneath a school of prey, which from the surface today, we suspect is the small, silvery fish, capelin. The whale then exhales a spiral of bubbles, which, as they float toward the surface, create a rising net that draws the prey into a tight cluster. Encircled in a curtain of bubbles, the prey are deceived into thinking there is a barrier – and no escape. Once the fish are corralled, the whales lunge upward through the now densely-packed fish, mouths agape, to swallow a large meal in a single gulp. From the drone, it quickly becomes obvious that the whales are bubble-net feeding in singles and in pairs. Though known to use bubble nets solitarily, it is largely considered a cooperative behaviour which requires precise timing, communication and a shared understanding among the whales. In groups, individuals are assigned different roles: bubble-blower, caller or lunger, and studies even suggest that whales vocalise specific calls to communicate during the process. The mechanisms of bubble-net feeding are interesting too, in that they are highly sophisticated acoustic and energy efficient strategies. Recent research has confirmed that these nets create a ‘wall of sound’ with intense sound pressure and particle motion along the spirals of bubbles, while keeping a central ‘quiet zone’, where the prey instinctively cluster.

Humpback whales are a species that ‘follow the food’, and dictated by seasonal changes in prey availability, undertake long distance migrations that match resource peaks. For those that migrate to Greenland, the distribution and availability of prey is closely tied to ocean temperatures and ice conditions. In the Arctic, life is dictated by the flow of its two main seasons, a long, dark 9-month winter, and a short 3-month summer. In the ocean, this bi-annual transformation has historically played out with a certain level of predictability. As the sea ice recedes at the end of winter, it triggers a series of ecological events that cascade through the food web. As sunlight penetrates the open water, it ignites a massive phytoplankton bloom – the foundation of the Arctic marine ecosystem. This bloom fuels the reproduction and growth of zooplankton, such as copepods and the small, fat-rich crustacean, krill, which, in turn, attract fish like capelin and herring.

At the apex of this food web stand the baleen whales, whose survival is inextricably linked to the abundance of prey below them. Bowhead whales, another species of baleen whale, having arrived in late winter to feed on copepods beneath the ice, generally depart Greenland in late May as the ice begins to break up. The bowheads are followed by the arrival of the sub-Arctic species, like humpback whales, who move in just as the waters open, to capitalise on the swarms of krill and the spawning aggregations of capelin that generally amass in shallow waters between May and July. This temporal handoff between Arctic and sub-Arctic species signals the ecosystem’s shift into summer.