Bubble Net Feeding
Clearly, the humpback whales are returning for a reason and it is evident that the geographic region from Caamano Sound to Douglas Channel is a vital feeding ground. In early spring, after the 3000-mile migration from the tropics, humpback whales have lost a large portion of their body weight. There is no food available in the warmer waters of Mexico and Hawaii so when they arrive up north they are in dire need of food. The feeding frenzy begins immediately and will last from dawn to dusk.
We are very fortunate in our research area as the most common form of foraging is bubble net feeding. During this feeding display they will cooperate in groups from 2 to 15 individuals. The technique they use to ensure each whale has the opportunity to feed is inspirational and spectacular to witness. Once every whale has taken a dive the true work begins, hundreds of feet below the surface. The whales will dive below a school of prey, and then slowly they begin a spiral dance upwards towards the surface, blowing bubbles in a circular motion forming a net. On the surface you will actually see a circle of bubbles form as the whales move in this spiral formation. The purpose of the bubbles is to congregate the school of herring and force them towards the surface near the centre of this circle.Then the feeding calls begin, long hollow calls, followed by higher pitched squeals.
The whales use these specific calls when they are feeding and the calls play a huge role in this feeding technique as they further congregate the fish. What we witness next at the surface is an explosion of air as these whales surface in the centre of this bubble circle, their mouths gaping wide open, full of small fish jumping for their lives.
Humpback whales have 14 to 35 throat groves that run from chin to navel. These grooves facilitate the expansion of the throat. This expansion allows for large volumes of water and food into the mouth. As the mouth closes the whale will press down with its tongue forcing all water out through baleen plates. These baleen plates hang in rows from each side of the upper jaw and act as a filter, keeping all the small fish from escaping. Baleen is made of a protein, referred to as keratin, which is both strong and flexible. With this innovative evolutionary adaptation the humpbacks feed on krill, and various species of small shoaling fish such as herring, pilchards and mackerel.
On the sidelines are a variety of humpback companions, such as seals, sea lions, Dall’s porpoise and an assortment of sea birds taking fish from the whales have been injured or left behind. We imagine, just like us, all these species are waiting for the arrival of this food frenzy so they may participate in one of the planet's most outstanding display of cooperative feeding.