From: http://www.afsc.noaa.gov/ABL/Humpback/AboutHumpbacks.htm#bubble
Occasionally, humpbacks in Southeast Alaska
will feed in coordinated groups using bubbles to trap fish at the
water’s surface. This behavio r is known as bubble net feeding. Bubble
net feeding involves anywhere from 4-20 whales all working together to
herd schooling fish into dense schools in order to maximize the feeding
productivity of the group.
While many other whales and other animals use bubbles to assist in prey capture, the specific methods used in this complex feeding strategy are unique to whales in Southeast Alaska and are seen only in certain areas and seasons. To summarize the bubble net technique; a group of humpbacks will dive down to herring schools where one whale (the bubble-blower) will release a ring of bubbles from its blowhole as it spiral beneath the prey. As this air rises to the surface, it creates a curtain of bubbles that acts as a physical barrier to frighten and retain the school of herring. Simultaneously, another whale in the group will produce resonating vocalizations, which also act to frighten the prey and trigger them to school up in tight balls within the bubble net. The whales then orient below the schooled fish and lunge, mouths open, to the surface through the center of the bubble ring, or bubble net. This motion drives the fish to the surface, where they are trapped from all sides (the surface of the water above, the bubble curtain on the sides and the open mouths of whales below). The whales will break the surface of the water in unison with mouths wide open, and then close their mouths while roll at the surface as they force the water from their throat cavity out through their baleen plates; the sieving process which allows them to swallow their catch without having to swallow excess saltwater.
While many other whales and other animals use bubbles to assist in prey capture, the specific methods used in this complex feeding strategy are unique to whales in Southeast Alaska and are seen only in certain areas and seasons. To summarize the bubble net technique; a group of humpbacks will dive down to herring schools where one whale (the bubble-blower) will release a ring of bubbles from its blowhole as it spiral beneath the prey. As this air rises to the surface, it creates a curtain of bubbles that acts as a physical barrier to frighten and retain the school of herring. Simultaneously, another whale in the group will produce resonating vocalizations, which also act to frighten the prey and trigger them to school up in tight balls within the bubble net. The whales then orient below the schooled fish and lunge, mouths open, to the surface through the center of the bubble ring, or bubble net. This motion drives the fish to the surface, where they are trapped from all sides (the surface of the water above, the bubble curtain on the sides and the open mouths of whales below). The whales will break the surface of the water in unison with mouths wide open, and then close their mouths while roll at the surface as they force the water from their throat cavity out through their baleen plates; the sieving process which allows them to swallow their catch without having to swallow excess saltwater.
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