Bubble net feeding is type of behavior known as social foraging. It is unique to humpback whales. Even though humpbacks are found throughout the world, this type of group feeding is not practiced by all humpback whales. It has been observed and documente in the literature in populations in Alaska, the Northeast Coast of North America, and the west coast of South America. Of all of the bubble net feeding groups, the population in Southeast Alaska is the best characterized. To say that this behavior has been well characterized would be incorrect. Even though it is an exciting and conspicuous behavior that has been captured on film many times, the mechanics and factors that determine bubble net feeding are poorly understood. AWF scientists are some of the most experienced observers of bubble net feeding in the world. National Geographic collaborates with AWF in order to observe and film this amazing behavior.
     First described in the 1980's by scientists such as Cynthia D'Vincent and Scott Baker, scientist have come to understand that group bubble net feeding is a group foraging behavior that is used to hunt and capture small schooling fish. Many species of marine mammals are known to utilize bubbles to catch prey, but what is unique about the way humpbacks use bubbles in and elaborate manner to manipulate the prey. We are unsure about what factors affect the formation and size of the groups, but it is clear that some members of bubble net feeding groups have specific roles within the group that are key to the groups' foraging success. Evidence suggests that there is one whale that blows the bubbles that manipulate the prey. The responsibility of that whale is to produce a curtain of ascending bubbles that create a wall through which the school of fish will not pass. An image from video that shows a whale producing bubbles can be seen in the image at the left. The bubble blowing whale probably has some idea where the prey are because it changes depth of deployment depending upon how deep the prey is positioned in the water. The bubble blowing whale begins by makes a long, curving line of bubbles that will break up as it rises to make a tall wall of bubbles rising to the surface. We do not know if all of the whales that forage socially take on the role of bubble blower, but it is clear that this role has special significance within the foraging group.
     While the whale that is making the bubble wall is busy with that role, the other whales in the group are together in a position that we think is somewhat removed from the bubble net being deployed. The group have dived down from the surface of the water in a relatively tight group. At the time the whales are diving as a group is when we obtain many of the fluke ID photos that we use to identify individual whales. Evidence suggests that the group positions themselves with the school of herring between them and the bubble blower.
     Once the group of whales is under water, one whale within the group initiates a series of vocalizations known as feeding calls. Recordings of these sounds can be heard on our recordings of whales page. We know that the herring move away from the source of the feeding calls toward the wall of bubbles. We do not know, if the feeding calls also serve as a communication among the whales. As the prey come close to the bubble wall, the bubble blowing whale encloses the wall of bubbles around them, creating a cylinder of bubbles with the fish trapped inside. A depiction of the complete bubble net can be seen in the illustration on the right. The whale in the picture is not in the correct position and is for illustrative purposes, only. The group of whales position themselves at the bottom of the cylinder and the herring are fleeing upward toward the surface.
     Somehow the group of whales knows when to move together up through the cylinder of bubbles. We do not know when the bubble blower joins the group, but it is a part of the lunging group. As the whales approach the surface, they open their mouths wide and aspirate from their blowholes. A depiction of an individual whale going through the motions of the coming to the surface can be seen to the left. As humpbacks open their mouths, their jaws are able to "unhinge" and extend to create a larger area for consuming prey. During the last few moments of what we call the group lunge, some other whales may join the vocalizing whale in a chorus of feeding calls. At this time the herring are trapped against the surface of the water, and video evidence suggests that they school may turn and move toward the whales, possible with the purpose of escaping by passing in between the whales that are coming at them. As this happens, the humpbacks bring their pectoral fins forward and flash the white underside at the approaching prey; this has been verified by National Geographic Crittercam footage. The frightened prey turn, once again toward the surface of the water and are in perfect position to be consumed by a big gulp of water and prey as the whales break through the surface of the water in an awsome spectacle of whales exploding out of the water.

     To accomodate all of the water and prey in their mouth, there is an area under the lower jaw, that is known as the buccal cavity. The skin around this cavity is pleated and will expand to accept thousands of gallons of water, much like the way the pouch of a pelican's beak can expand to take in fish and water at the same time. When the mouth is full, the whale will close its mouth and force all of the water out by straining it through the baleen that hangs down from the palate of its mouth. This keeps all of the food inside while getting rid of the water. At this point, the whale can swallow its mouthful of food. Pictures of the distended buccal cavity on a whale and a whale forcing water out of its mouth can be seen below.
     As you can see from the pictures below, the sight of a group of whales lunge for food at the surface of the water is a breathtaking event. If you click on the pictures, you can see larger versions.

     People often ask us if we are nervous about whales coming up underneath our small boats when we are out observing bubble net feeding. We doubt that a whale would ever come up under our boat for several reasons: 1) humpbacks do not chew their food, they swallow it whole, 2) evident suggests that baleen whales do not have a natural way to spit something undesireable out of their mouth, therefore they have to go through the effort of getting it out some other way, 3) humpback whales have a small throat, no wider than two widths of a human hand, so large items in the mouth could choke a whale, and 4) whales appear to be fairly aware of their environment when foraging, in Southeast Alaska many different things could be found in the water such as logs, and that would be something that whales would want to avoid getting in their mouths or bumping up against.
     If we are patient and quiet while recording feeding calls, we are sometime fortunate enough to see a group lunge very close to the boat. In the picture below, we had been observing quietly with our engine off for about 30 minutes, when this exciting moment occurred.

     In Southeast Alaska, the prey is primarily Pacific herring (Clupea harengus pallasi). It stands to reason, that this type of feeding is practiced in locations where the herring occur in numbers sufficient to warrant expending energy on hunting such prey, since large numbers of small fish are needed to sustain such large predators. Within our field site, evidence suggests that herring occur at high density in widely dispersed patches throughout much of the summer in Chatham Strati. Whales that frequent Chatham Strait are often seen participating in bubble net feeding. Because of the prey dynamic in Chatham Strait whales can be difficult to find. In Frederick Sound, dense herring schools are less frequent and more ephemeral occurrences. Some summers can proceed without observing whales in Frederick Sound bubble net feeding at all, while in other years social foraging is common. As an alternative to schooling fish, Frederick Sound offers a rich population of krill. This prey dynamic in Frederick Sound, often means that whales can be seen easily but are often foraging individually; groups will form temporarily to take advantage of schools of fish, but often the pods will break up quickly to return to individual foraging.