Wednesday, May 07, 2014

PBS Nova: "Why Sharks Attack": Jaws revisited


PBS Nova tonight premiered its documentary “Why Sharks Attack”, pretty much the science behind “Jaws”.  The link is here.   

Most of the work in the film was done in the waters near Western Australia (all of which looks like the American SW without many mountains), especially Shark Bay. 
  
Sharks have a variety of ways that they use their senses, which is reflected in their brains.  The great white shark uses vision, especially for prey above them, and can see only shades of green.  But other sharks use electrical potential to detect prey.  The great white also has internal temperature regulation like warm=blooded mammals. 
  
  
The documentary also showed more exotic sharks, like hammerheads and related sting rays.  The shark is over 400 million years old.  The great white can live about 50 years.  Some sharks are social, and certain parts of their brains are more developed as a result.
  
I remember reading Peter Benchley’s “Jaws”, and he made fun of his characters in that novel, especially the chagrin of the policeman protagonist. 
  
In his “Free Fish” video, actor Reid Ewing actually plays with a sting ray for a moment before saying “I’m done with you.”  He also says “fish are like people…”
  
But is a shark a true fish?  It has cartilage, but not full bone, and it has some of the biological aspects of mammals.  It is an example of evolution going in a totally different – and reproductively successful – direction. Dolphins and orcas (mammals) are like people, but sharks aren't. 
      

The show presented a few people who had been wounded by sharks and recovered.  But people kill a lot more sharks (when nobody notices) than sharks kill people (when we do notice).  If we venture into their homes, we can’t blame them for becoming alarmed.  

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