A pair of humpback whales (Megaptera novaeanglia) blowing and sounding, Tenakee Inlet, Southeast Alaska, USA.
Humpbacks have an enormous lung capacity, which makes it possible for them to dive for long periods, often in excess of 20 minutes, These extended dives allow the animals to descend to deep water for foraging (up to 500 ft - 150 m). When the whale surfaces to breathe, it only has a few moments to exchange the air in its lungs, so it must exhale with tremendous force. The force of this exhalation vaporises the seawater that surrounds the blowhole and creates a "blow". This vertical plume of water vapour is usually the first indicator that a whale is in the area, and can usually be seen and heard over long distances. On several occasions I paddled stealthily up to a whale resting or sleeping on the surface just to be able to observe the blowhole in operation at close quarters, and was amazed at the power and speed that the blowhole opens and shuts during the exhalation and inhalation, and the explosive force of the breath rushing out and fresh air rushing back in.
I observed them often sleeping in the afternoon, their rotund backs completely motionless with their flukes and long pectoral fins hanging down. Whales and dolphins don't sleep for extended periods the way that we do but just take short naps. To avoid drowning during sleep, it is crucial that marine mammals retain control of their blowhole. The blowhole is a flap of skin that is thought to open and close under the voluntary control of the animal. Although still a matter of discussion, most researchers feel that in order to breathe, a dolphin or whale must be conscious and alert to recognize that its blowhole is at the surface.
- Duncan Murrell
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- Humpback Whales - Blowing and Sounding