Tuesday, November 9, 2010

Building dolphins

Yesterday, I built a dolphin. I made it as round as a ball but gave it a big tail for propulsion. It moved okay, but unfortunately couldn't turn fast enough to avoid hitting the underside of a propeller driven boat and exploding.

It was sad. Possibly, no one should employ me as a substitute god quite yet.

To console myself, I went to chill out in the heart of a blue whale. Weighing over 150 tons and measuring up to 39 m in length, the adult blue whale is the largest mammal that has ever lived. A 1:1 scale model of its heart is therefore a perfectly comfortable place to sit, at least once I had shoved the kids out through one of the valves.

I was at the Ontario Science Centre which had an exhibition running on whales. In pride of place (by necessity of its size) was the skeleton of a sperm whale whose 18m length stretched the length of the hall. It might fall short of its blue whale cousin, but the sperm whale is the largest toothed predator, even if it does use its teeth mainly for filtering and biting other males in fights. Blue whales have baleen plates that resemble giant brushes, rather than teeth, which filter huge quantities of water for krill; a technique known as 'lunge feeding'. Sperm whales and other toothed family members, such as dolphins, feed on individual prey such as giant squid. Because of this, the sperm whale also has the honour of having the largest nose that is actually a massive echolocation device which it uses to hunt squid down to depths of 2000m. By contrast, the human record for a dive is 82m. Rather than a tool for hunting, the noises made by baleen whales are used for communication, such as the humpbacked whales' song. Its low frequency allows the sound to cover huge distances so these solitary beasts can contact one another.

After I'd mentally redesigned a whale's insides into an entry for 'changing rooms', I started to wonder about how such a humongous mammal ended swimming. After all, one could hardly picture an elephant taking this as a personal challenge. I originally presumed that when mammals first left the ocean, a off-shoot stayed behind. These would then become whales, while the land-lovers developed two legs, shoved them under a computer desk and became graduate students wondering why they left the ocean and if it was too late to change their mind. In fact, it turned out I was wrong. The exhibition showed that whales developed from land animals who moved into the sea to take advantage of the food source there. Fossils exist of deeply confused creatures known as 'ambulocetus natans' (literally 'walking whale') that could both walk and swim. They appeared to hear sound through their lower jaw which was transmitted to the soft tissue leading to the ear in an early version of the echolocation mechanics of their descendants.

More soberly, another board discussed the problem of beached whales. In New Zealand, they have had to deal with a mass beaching of sperm whales whose huge bulk makes refloating almost impossible. Internal damage from the beaching is highly probable and the mammals rapidly overheat when stranded. When this happens, a fast, humane death is considered preferable and is carried out using a specialised device known as SWED: Sperm Whale Euthanasia Device. This is a single-shot anti-tank rifle, the kind of weapon usually designed to penetrate the armour of tanks. 

On a more cheerful note, New Zealand is also home to the smallest of the whale family, Hector's dolphin, whose length is just 1.5m. That's just over a 5th of the size of a newborn blue whale, which weights 3 tons at birth. I'm thinking not a crib from Ikea.

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