Humpback whales use their pectoral fins like barriers and spoons

Humpback whales are known for their sophisticated hunting and feeding strategies. In particular, setting nets of air bubbles to capture fish and herd them to the surface is one of the most interesting strategies of these giant marine mammals. Another feature that makes humpback whales special are their powerful pectoral fins. Until now, it was thought that these limbs, up to 5 meters long, were used for propulsion. But a researcher in Alaska has observed how the whales use their flippers to hunt and eat.

The footage, captured by Madison Kosma, a student at the University of Alaska, Fairbanks, using a drone in spring 2018, clearly shows a humpback whale using its powerful pectoral fins as a barrier and spoon to bring young salmon into its gapping mouth. The whale first used the so-called “bubblenet feeding” strategy. In the process, the whale dives in a circle around the school of fish and releases its breath so that the air bubbles form a net around the school. The confused fish push up instead of through the bubbles and the whale only has to swim into the shoal from below with its mouth open.

Kosma observed that just before the whale comes to the surface, its pectoral fins spread out like a barrier, enclosing the school. She had observed this behavior two years earlier at a salmon nursery near Baranof Island, Alaska, but never had a good look at what was actually happening. It wasn’t until 2018 with the use of a drone that the student was able to get a clear view of the behavior from above. “For the first time, scientists have been able to observe proper recordings of a very complex process of whales fishing,” Kosma writes in her paper, which appeared this week in the journal Royal Society Open Science.

Kosma and her colleagues also discovered that the whales, for one, hunt on hunt and form nets on their own at the site. This is unusual, since network formation is actually known as a cooperation technique. On the other hand Kosma observed from the recordings that the whales not only enter the school steeply from below but also use their fins sideways. Closer examination of the conditions showed that the amount of light and the visibility under water probably play a role in this. The vertical ascent was used in direct sunlight, the lateral use only when there is shade on the water or when avoiding an obstacle. The researchers suspect that the fish are confused by the bright underside of the fins and the fins form a current toward the mouth, which is dark and signals safety, forms and the fish “voluntarily” swim there. But the scientists emphasize that their observations apply only to the whales in this region. Here, millions of young salmon are released from the nursery into the wild every year. and the whales must have learned this. Richard Connor, a cetacean expert at the University of Massachusetts who has seen the footage says that humpback whales use their pectoral fins for many behaviors. He suspects that the use for hunting favored the development of such long fins. “It is likely that hunting success is a major factor of selection that favored the animals with longer pectoral fins. The whales have been fishing this way for a long time. Now we finally have aerial photographs that let us see that, too.” But whether other humpback whale populations use fins in a similar way when feeding remains to be seen.

Humpback whales are remarkable animals in many ways. They migrate thousands of kilometers each year from breeding sites in the warm and tropical zones to feeding grounds in the Arctic and Antarctic; They have a distinctive communication and songs, which they can vary and calves learn from their mothers the routes and resting places during their migration. during migration; Young animals remain in Antarctica along the pack-ice boundary for several years after weaning. Of all the whale species that have been hunted, most humpback whale populations have recovered the best; They exhibit various behaviors such as breaching, fin pointing, fluking, and spyhopping that cannot yet be fully explained. Researchers still have a lot to to learn about these giant marine mammals.