Posted by S.SURYA NARAYAN on Oct. 1, 2013, 10:21 p.m.
Whales take in air less frequently than land mammals, and they can hold their breath for extraordinarily long periods during their dives. Although their lung capacity is no greater than that of land mammals of equivalent size,whales take deeper breaths and extract more oxygen from the air they breathe. Unlike the seal, which exhales before diving, a whale's lungs are still partially inflated. The whale's nostrils are modified to form a blowhole at the top of the head. The skin immediately surrounding the blowhole has many specialized nerve endings, which are very sensitive to the change as the blowhole breaks the water. The whale often breathes in and out again very rapidly, in the fraction of a second that the blowhole is above the surface. The blowhole is closed when the animal is submerged. When a whale surfaces and exhales, a spout of water 'flow' can be seen.