The enigma of the shark

StoryImage( ‘/Images/Story//Auto-img-113459307111427.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘The writer watches a shark glide by behind thick plate glass at the National Aquarium.’);

Beyond a doubt, the marine animals most feared by beach goers, swimmers, and surfers are the some 300 species of sharks found in the seven seas. Many times along the Gulf of Mexico and eastern U. S. coasts, I have seen utter panic develop by swimmers at the sight of the dorsal fin of a porpoise gleefully cavorting in the water off shore. Despite the vast amount of fiction, legend, horror stories and wishful thinking written on the relationship of sharks to humans, there are relatively few facts available on the subject.

Public opinion concerning shark attacks on humans seems to range all the way from “all sharks are dangerous,” to “no shark is dangerous to man.” Scientific evidence indicates, however, that the fact of the matter is to be found somewhere between these equally untenable theories.

Make no mistake about it: under certain circumstances, a few species of sharks may attack humans with devastating consequences. But, on a worldwide basis only 30 or so documented attacks are reported each year, with the majority occurring in Australian or South African waters. The chance of you being a victim of a shark attack in the waters of the North American coasts are extremely slim, regardless of the myths created by Hollywood script writers.

Shark experts agree that three species are responsible for the vast majority of documented attacks on humans: great white shark, tiger shark, and the hammerhead shark. Other species including the lemon, mako, blue, sand, nurse, and white-tipped sharks have been rarely incriminated. It is a wise person, however, who heeds the warning of “never trust any type of shark.”

Sharks first appeared in the oceans of the Earth some 300,000,000 years ago, and have reigned supreme in that environment ever since. The forces of biological evolution have molded them into the ultimate predator with no natural enemies except man. They have remained relatively unchanged for the past 80,000,000 years. It is hard to improve on perfection.

Sophisticated research over the past 30 years or so has revealed some amazing facts about these so-called primitive animals. One newly established fact is that sharks are not long-range prowlers of the oceans of the Earth. Rather, they have a definite, somewhat limited, home range. It is now believed that when a shark attacks a human, it is usually not out of hunger as was formerly believed, but, rather, as a response to an invasion of the fish’s personal territory.

Studies at the University of Miami have shown that sharks are resistant to all types of organisms that cause disease. Their blood contains primitive antibodies that even destroy certain human viruses and the bacteria causing a type of food poisoning in man; disease agents they have not and will never encounter.

Their sense of smell can readily detect one part of blood in 10,000,000 parts of water, and their sense of hearing can pick up low frequency sound waves, such as those of a struggling fish more than a mile away.

The Swedish naturalist Carolus Linnaeus suggested in 1758 that a great white shark’s tummy may have been Jonah’s residence for three days. Why not? Some of these monsters attain a length of 25 feet or more, and in the 18th century, a full suit of armor was recovered from the stomach of a great white. Other bizarre items like a stuffed penguin, a car license plate, a handbag containing three silver dollars and a powder puff, 24 bottles of Vichy water, numerous pairs of boots and shoes, and a tomcat have been recovered from sharks caught off the coast of Southern California by researchers at Stanford University. An extinct close relative of the great white could have held several Jonahs. It had huge teeth, some 4 inches long and more than 5 inches wide at the base. It has been determined that this extinct beast was at least 60 feet long and weighed more than 50 tons.

If you would like to come nose to nose with a variety of shark species and have no fear of being attacked, the next time you are in Baltimore, go to the National Aquarium to view an outstanding exhibit of living sharks in a natural setting.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

From the Dec. 14-20, 2005, issue

Enjoy The Rock River Times? Help spread the word!