Cetaceans
Section: Theater Essays
To make this easier, the cetacean's blowholes have moved to the top of its head, giving it a quicker chance to expel the stale air and inhale fresh air. When the stale air, warmed from the lungs, is exhaled it condenses and vapourises as it meets the cold air outside. This is rather like when you breathe out on a cold day and a small cloud of warm air appears. This is called the 'blow', or 'spout', and each cetacean's blow is different in terms of shape, angle and height. This is how cetaceans can be identified at a distance by experienced whalers or whale-watchers. The cetacean's eyes are set well back and to either side of its huge head. This means that cetaceans with pointed 'beaks' (such as dolphins) have good binocular vision forward and downward, but others with blunt heads (such as the Sperm Whale) can see either side but not directly ahead or directly behind. The eyes shed greasy tears which protect them from the salt in the water, and cetaceans have been found to have good vision both in the water and out.
Akin to the eyes, the cetacean's ears are also small. Life in the sea accounts for the cetacean's loss of its external ears, whose function is to collect sound waves and focus them in order for them to become strong enough to hear well. However, sound waves travel faster through the water than in the air, and so the external ear was no longer needed, and is no more than a tiny hole in the skin, just behind the eye. The inner ear, however, has become so well developed that the cetacean can not only hear sounds tens of miles away, but it can also discern from which direction the sound comes. Cetaceans use sound in the same way as bats - they emit a sound, which then bounces off an object and returns to them. From this, cetaceans can discern the size, shape, surface characteristics and movement of the object, as well as how far away it is.
This is called sonar, or echolocation, and with it cetaceans can search for, chase and catch fast-swimming prey in total darkness. It is so advanced that most cetaceans can discern between prey and non-prey (such as humans or boats), and captive cetaceans can be trained to distinguish between, for example, balls of different colours, sizes or shapes. Cetaceans also use sound to communicate, whether it be groans, moans, whistles, clicks or the complex 'singing' of the Humpback Whale that is becoming so popular on wildlife documentaries and relaxation tapes. Feeding When it comes to food and feeding, this is where cetaceans can be separated into two distinct groups.
The 'toothed whales' or Odontoceti have lots of teeth that they use for catching fish, squid or other marine life. They do not chew their food, but swallow it whole. The cetaceans in this group include the Sperm Whale, dolphins and porpoises. The 'baleen whales' or Mysticeti do not have teeth. Instead they have plates made of keratin (the same substance as our fingernails) which hang down from the upper jaw. These plates act like a giant filter, straining small animals (such as plankton, krill and fish) from the seawater. Cetaceans included in this group include the mighty Blue Whale, the Humpback Whale, the Bowhead Whale and the Minke Whale.
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