most common. Usually the lower teeth are used first in feeding; solitary upper tooth slashes might indicate
attacks unrelated to feeding. Up to 60% of wounds involve only the upper teeth. At the moment of the strike
the shark rolls its eyes back in the socket and uses the ampullae of Lorenzini to home in on the victim.
Sharks are selective feeders with clear dietary preferences. They commonly attack young, old, injured,
or sick prey. Sea turtles, squid, penguins, seals, and stingrays are consumed in preference to humans. Sharks
often eat other sharks. The great white shark cruises along the bottom of the ocean preparing to launch an
attack on an unsuspecting surface animal. It can strike with enough force to lift the animal out of the water
and breach itself, tearing a 50 lb. chunk of flesh from its victim or even decapitating the animal. The
cookiecutter (or cigar) shark Mirounga angustirostris or Isistius brasiliensis creates a circular crater-like
wound approximately 5 to 6 cm in diameter when it attacks its pinniped prey. Sharks have short intestines,
seem to be able to selectively digest ingested foodstuffs, and may be able to keep portions of what they ingest
intact for prolonged periods of time, perhaps as a method to regulate nourishment.
It is difficult to generalize about shark attacks on humans. Current explanations suggest that frightened
persons are more likely to be targets of aggression. This has been demonstrated in the case of the gray reef
shark, Carcharhinus amblyrhynchos. Aggression may be aggravated by purely anomalous behavior, the
violation of courtship patterns, or territorial invasion. More docile behavior tends to be the rule with other reef
sharks, such as the silvertip (Carcharinus albimarginatus), blackfin (C. melanopterus), or whitetip
(Triaenodon obesus). The legs and buttocks are most commonly bitten, perhaps an indication of dangling legs
or buttocks displayed by an abalone diver facing a rock or ledge. Since sharks don't chew their food, their
method of biting and rolling or thrashing allows flesh to be stripped from the victim. Teeth may be embedded
in prey, but fractured bones are surprisingly rare. A large shark can attack and sink a boat, but may wait to
return and consume the human boaters.
The great white shark (Carcharodon carcharias) is a man-attacker but probably not a man-eater. This
statement reflects the observation that this highly feared animal (which has been observed at a length of 21
feet and an estimated weight of 4500 pounds; it can probably attain a length of approximately 25 feet and a
weight of 5500 pounds) usually releases its victim following a single "inquisitory" bite, after it recognizes that
a mouthful of neoprene, fiberglass, or lead weights is not normal dietary fare. This is small consolation to the
unfortunate victim, who may have an entire hemithorax or limb removed. The great white shark has only
recently been closely observed in the wild and is thus the subject of much speculation about predation
strategies. The feared trait of the great white sharks is that they initiate contact with man. Their unpredictable
nature ranges from a seemingly docile approach to a research boat to a powerful attack on a surface sea lion.
Adults feed largely on pinnipeds; the bite-and-spit behavior is considered a means of avoiding injury from
struggling prey. One theory is that a shark that largely consumes a human victim does so because the victim
was solitary in the water. Breath-hold diver behavior and the similarity of the silhouette of a contemporary
surfboard to that of a surface seal may be responsible for attacks on humans. Most attacks on humans occur at
the water's surface. One fatal attack in 1989 with two victims was on sea kayakers off the coast of southern
California. At the time of this writing, there have been (since 1876) approximately 250 documented attacks by
great white sharks upon humans, with approximately 65 fatalities.
Shark attacks have occurred from the upper Adriatic Sea to southern New Zealand, with most between
latitudes 46
o
N and 47
o
S. The odds of being attacked by a shark along the North American coastline are
approximately 1 in 5 million. The danger is greater during the summer months (more persons in the water), in
recreational areas, during late afternoon and nighttime feeding, and in murky warm (68
o
F or 20
o
C) water.
White sharks frequently venture into colder water, and attacks have occurred in waters as cold as 50
o
F (10
o
C). The frequency of shark attacks off the northern California coastline appears to be increasing, particularly
with respect to the great white shark. Contrary to the findings of worldwide shark attack analysis, attacks in
northern California occur more frequently in clearer water at temperatures of less than 60
o
F (16
o
C). Shark
attacks in Hawaiian waters are relatively rare, with the exception of recent events.
Although most attacks occur within 100 feet of shore, it is believed that the danger is greater further
out, in deep channels or dropoffs. Because of their ability to detect contrasts, sharks have a predilection to
attack bright, contrasting, or reflective objects. Movement is an added attraction to sharks, which have been
known to bite surfboards, boats, and buoys. Recent shark attacks in northern California coastal waters
involved swimmers on surfboards (black on white) who entered migratory elephant seal (shark food) habitats.
