nonprofit marine research institution which operates The Center for Shark Research, focused on behavioral
and medicine-related research. The Shark Research Institute publishes that it maintains a database that
"contains more than 2,000 incidents involving divers, surfers, swimmers and fisherman," with a "network of
investigators throughout the world that actively investigates attacks." Other records of shark attacks are
maintained by the California Department of Fish and Game and the Waikiki Aquarium in Honolulu, Hawaii.
Although dreaded, sharks are among the most graceful and magnificent denizens of the deep. Sharks
may be found in oceans, tropical rivers, and lakes. The bull shark Carcharhinus leucas is a frequent river
inhabitant. Sharks range in size from 10 to 15 cm (Squaliolus laticaudus) to over 15 m and more than 18,144
kg (the whale shark Rhincodon typus, fortunately a plankton feeder.
Some 32 of the currently known 375 (approximate) species of sharks have been implicated in the 100
to 150 shark attacks upon humans that are estimated to occur annually worldwide, and another 35 to 40
species are considered potentially dangerous. U.S. coastal waters may be the setting for nearly one quarter of
the attacks. Six to 10 deaths from shark attacks are reported worldwide each year. The most frequently
implicated offenders are the larger animals, such as the great white, bull, tiger (Galeocerdo cuvier), and
oceanic white tip sharks. Sporadic attackers include the gray reef, blue, shortfin mako, dusky, hammerhead,
lemon, Ganges River, Galapagos, spinner, sand, nurse, blacktip, blacknose, blue, bronze whaler, and ragged
tooth sharks. Tiger sharks were identified in a cluster of attacks around the Hawaiian Islands in the winter of
1993.
Sharks are carnivorous; many are apex predators. Their danger to humans results from the
combination of size, aggression, and dentition. Some sharks, such as the giant whale shark (the largest fish at
50 feet in length and more than 40,000 pounds), eat plankton and use their teeth as filters. Even small sharks
can be powerful and destructive. The white shark is responsible for more attacks than any other species,
particularly in the waters of southern Australia, the east coast of South Africa, the middle Atlantic coast of
North America, and the American Pacific coast north of Point Conception, California. Attacks by great white
sharks off the coast of northern California has led to the designation of a "red (or bloody) triangle" bordered
on the north by Pt. Reyes and Tomales Bay through the Farallon Islands to the west and down south to Año
Nuevo and Point Sur facing the Monterey Bay. This is a breeding area for elephant seals (Mirounga
angustirostris), which yield 200-pound pups, perfect food for the immense predators.
The tiger (Galeocerdo cuvieri) (up to 18 feet and 2000 pounds) and bull (Carcharinus leucas) sharks
are the next most dangerous with regard to attacks on humans. The great hammerhead (Sphyrna mokarran)
has a reputation as a man-eater in equatorial waters. Scattered over its entire undersurface, the hammerhead
has ampullae sensitive to electromagnetic fields, which in combination with its highly developed sense of
smell may make it a superior predator.
In an analysis of California attacks, Miller and Collier attributed unprovoked attacks north of San
Miguel Island to white sharks, while those south of this area involved members of the families Carcharhinidae
(requiem sharks), Sphyrnidae (hammerheads), and possibly Squatinidae (angel sharks).
As previously noted, sharks are well equipped in the sensory aspects of feeding. They seem
particularly able to avoid detection by potential prey, by virtue of coloration and a stealthy approach. Sharks
feed in two basic patterns: (1) normal or subdued, with slow, purposeful group movements, and (2) frenzied
or mob, as the result of an inciting event. The latter is precipitated by the sudden presentation of commotion
or food/blood in the water. Frenzied behavior is enhanced by the proximity of other sharks in large numbers.
In a frenzy, sharks become fearless and savage, snapping at anything and everything, including each other.
After a shark decides to attack, it "postures," swimming erratically with elevated snout, arched back, pectoral
fin depression, stiff lateral bending of the body, and rapid tail motion, in contrast to its normal sinuous and
graceful swimming style. In bursts of speed a shark can use its powerful caudal fin muscles and attain speeds
in the water of 20 to 40 miles (32 to 64 km) per hour. As the Carchariniform shark prepares to strike, it
rapidly opens and closes its jaws (up to three times each second), depresses the pectoral fins in a braking
action, and elevates the head. During a bite the shark shakes its head and forebody in an effort to tear flesh
from the victim. The shark may bite and spit to mortally wound the victim before eating it. Sharks swallow
food whole without chewing it. Analysis of human remains recovered from a tiger shark indicate that the
human victim was dismembered and then swallowed and digested. It is difficult to postulate hunger as the
sole attack motive, since more than 70% of victims are bitten only once or twice. Hit-and-run attacks are
