Bubble-net feeding is a bizarre and complicated feeding practice engaged in by humpback whales and Bryde’s whales. It is one of the few surface feeding behaviors that humpback whales are known to engage in. This type of feeding is often done in gatherings. The group size can range from a minimum of two or three whales joining and up to sixty at one time.
How it is done?
Bubble-net feeding is a cooperative feeding method used by groups of humpback whales. This practice is not instinctual, it is learned. Not every population of humpbacks know how to bubble net feed, according to some studies. After observing diverse populations it is apparent which whales know how to create a bubble net and which do not. To be successful, they must learn the method. Humpback whales use vocalizations to talk to one another and effectively and efficiently execute the bubble net so they all can feed. As the group circles a school of small fish such as salmon, krill, or herring they use a team effort to disorient and corral the fish into a net of bubbles. One whale will typically begin to exhale out of their blowhole beneath the surface at the school of fish to begin the process. More whales will also start to blow bubbles while proceeding to circle their prey. They corral the fish into a tight circle while creating a net of bubbles to surround the fish and keep them from leaving. The size of the net created can range from three to thirty meters in diameter. One whale will sound a feeding call, at which point all whales simultaneously swim upwards with mouths open to feed on the trapped fish. As the whales swim up to the surface to feed they can hold up to 15,000 gallons of sea water as they use their baleen plates to strain the water to get the greatest amount of fish they need. Humpback whales have 14 to 35 throat canals that run from the top of the chin down to the navel. These grooves allow the mouth to expand. When they swallow they stream the water out through their baleen as they ingest the fish. The fish that they ingest are also a cause of hydration for them. Bubble netting is an excellent and vital feeding method exhibited by humpback whales to feed multiple mouths at one time.
Humpback whales are solitary creatures and do not always feed in large groups. They can perform a comparable method of surface feeding but it is referred to as lunge feeding. It is likewise performed as the whale dives down beneath a school of fish and rises to the surface with its mouth wide open. Once it reaches the surface it will swallow, remove the fish from the saltwater, and spit the excess water.
Theories
This system of feeding, which is unusual and unique to humpback whales, has sparked lots of interest. There has been some consideration behind the net of bubbles and how fish are confined within. One study suggests that it is the acoustics from the exhalations from the whales that traps the fish. It is thought that within the circle it is still but outside the sounds have such high intensity that it is nearly impossible for fish to escape.
There are also a multitude of theories behind why humpback whales use bubble netting as a feeding method. The earliest documentation of this feeding behavior was recorded in 1929 from the Norwegian Sea. They speculated that it was comical behavior between the whales and a form of socializing. Exchange in environmental factors over the years has also been discussed as a possibility behind why this feeding method was created. The most popular theory behind bubble net feeding is one of survival. After being hunted to near extinction it is believed that humpback whales developed this method of feeding so many whales as potential can feed in a short amount of time.
