This article is from the July 30, 2001 issue of Time and was written following what appeared to be an increasing number of shark attacks, primarily on the Florida coast. I thought this may be timely as we head towards summer and the beach.
The most interesting aspect of the article is a detailed description of the shark sensory system. First, in the snout region are a network of pores and long jelly-filled canals sharks use to detect weak electrical impulses and is sensitive enough to detect the fields generated by other creatures as they breathe. There is also an extensive lateral line system. Similar to a cat's eyes, sharks have a special reflective layer behind the retina that enables them to see in dim light, although the shark must move it's head from side to side to see what is directly in front. Sharks also have extremely sensitive ears that can detect the sound of a struggling fish up to 600 yards away and an acute sense of smell that can detect concentrations of blood as low as one part per million. All these senses combined make it very unlikely that a mature shark ever attacks a human by mistake.
The three shark species that most often attack humans (tiger sharks, great white sharks and bull sharks) all have different feeding patterns and modes of attack.
The great white, the most lethal of the bunch to humans, usually attacks by shooting up vertically from about 30 feet under the water. They have been seen leaping up to 15 feet in the air with a seal munchie. The ones most often responsible for attacking humans are in the 8 to 12 foot range, juvenilles that are making the transition from eating fish to seals. These are the only bunch that are considered to be attacking humans out of mistaken identity. "Jaws"-sized sharks have much better command of their senses. Of the three species mentioned, they are the only ones that hunt in the middle of the day (surfers on the California coast beware).
Attacks by tiger sharks have been on the rise in the Hawaii area and speculation is that this is due to an increased number of their natural prey, sea turtles, that are coming in to shore. Tiger sharks are not known to be territorial but they are persistent and will return repeatedly to gnaw away at a victim. The best way to avoid a tiger shark is to stay out of the water during the early morning and evening hours and especially during the season for turtles to come ashore to lay eggs.
Bull sharks have the highest level of testosterone of any other creature, land or sea. There is also speculation that this is what drives them to their territorial behavior and to be extremely aggressive (this is the most frequent culprit in the Florida area). The bull shark is the only large shark that prowls in shallow water (an eight year old boy who was almost killed was in only two feet of water)and that regularly traverse into fresh water. They have been sighted (and attacked) as far up the Mississippi as St. Louis, Mo. They are far less discriminant about the type of prey, often eating cans or shoes, but they also hunt mostly in the morning and evening hours.
How to avoid becoming shark food? Besides staying out of the water altogether, be aware of species of sharks in the area and avoid the water during their peak feeding times, don't swim in the ocean if you have any type of cuts or wounds, and most important............remember, you still have a 30 times greater chance of being struck by lightening.
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