Humpback whale's bubble net

The humpback whale (Megaptera novaeangliae) is a species of baleen whale. The adult ranges in length from 12–16 metres (39–52 ft) and weight approximately 36,000 kilograms (79,000 lb). 

A humpback whale shot in water. From Wikimedia Commons.

One of the attractive feeding techniques of humpback whales is the bubble net. A group of whales swim in a shrinking circle and blow bubbles below a school of prey. The formed bubble net confines the school of fish within a limited volume. The diameter of the bubble net could be up to 30 metres (98 ft). 

Humpback whale's hunting technique. Video from YouTube.

Bubble ring created by humpback whale. Adapted from National Marine Mammal Laboratory.

Using a crittercam attached to a whale's back, the secret of the talented feeding method of humpback whale has been revealed by National Geography. Firstly, a group of whales dive deep under a school of fish and form a circle. Then they blow their breath out to form a bubble net. Finally, the whales suddenly swim upward through the bubble net with mouths open and swallow a large amount of fish in one gulp. During the process, each humpback has a specialized task, e.g. blowing the bubbles, going down and herding the prey towards the surface and screaming sound to force the prey into the confines of the bubble net. 

A recent study by Wiley et al. (2011) (also introduced in ScienceDaily) found more information about the bubble net. Three-dimensional images of whale swimming behavior and bubble release are recreated based on collected data (e.g. depth and orientation in 3-D) using digital suction cup tags attached to whales. They identified a new novel behavior called "double-loops", which consist of one upward spiral to corral the prey and a second upward lunge to capture the corralled prey. The study also reported that at least two individual humpback whales are necessary for bubble net feeding. Furthermore, the humpback whales do not rob the prey from other's bubble nets.

Bubble net formed by humpback whale. Courtesy of Brill.

Humpback whale is not the only talent on the use of bubbles. Dolphins can also make amazing vortex ring, a toroidal shape of a cloud of bubbles moving along the fluids.

Vortex ring by a dolphin. YouTube.

References and further readings

David Wiley, Colin Ware, Alessandro Bocconcelli, Danielle Cholewiak, Ari Friedlaender, Michael Thompson, Mason Weinrich. Underwater components of humpback whale bubble-net feeding behaviour. Behaviour, 2011; 148 (5): 575 DOI: 10.1163/000579511X570893

Mercado E III, Herman LM & Pack AA (2003). "Stereotypical sound patterns in humpback whale songs: Usage and function," Aquatic Mammals 29 (1): 37–52. doi:10.1578/016754203101024068. Retrieved 3 April 2007.

http://www.dosits.org/animals/useofsound/animalsusesound/