On August 15, 1987, Craig Rogers, a landscape contractor then living in Santa Cruz, California, paddled out to go surfing at a nearby break. It was 7:30 a.m., Rogers was sitting up on his board, legs dangling over each side, searching the horizon for the next set of waves. Abruptly, he noticed his board stopped bobbing in the water.
"I looked down and my eyes filled with a sight of instantaneous horror," said Rogers. A great white shark was biting his board just in front of his left hand; the head was almost three feet (one meter) across. "I could have touched its eye with my elbow."
The shark had surfaced so quietly, Rogers hadn't heard a thing. He flung up his hands, accidentally grazing two of his fingers along the shark's teeth. "I yelled in terror and slid off the board to the opposite side," Rogers explained in a written report made just after the attack.
He was bleeding when he entered the water.
Submerging to his shoulder, he watched the shark gently release his board and sink like a submarine, disappearing beneath him. Later analyses of the puncture marks on his board suggest the shark was 17 feet (5 meters) in length.
"It is typical for a great white to swim up to someone at a relaxed pace, take a bite, then swim off," said Collier. This contrasts with the torpedo-like attacks on the seal, suggesting that the shark's goal is not predation.
Teeth Like Hands
"Great whites are curious and investigative animals," said Martin. "That's what most people don't realize. When great whites bite something unfamiliar to them, whether a person or a crab pot, they're looking for tactile evidence about what it is."
A great white uses its teeth the way humans use their hands. In a living shark, every tooth has ten to fifteen degrees of flex. When the animal opens its mouth, the tooth bed is pulled back, "causing their teeth to splay out like a cat's whiskers," said Martin.
"Combine that with the flexibility of each tooth, and you realize a great white can use its jaws like a pair of forceps. They're very adept at grabbing things that snag their curiosity."
Great whites are also sharp sighted, further evidence that they do not mistake humans for other prey. Scientists believe that sharks see as well below the surface as humans do above it. And they see in color.
"I've seen these sharks swim 70 feet (21 meters) to the surface to investigate a piece of debris no bigger than the palm of my hand," said Martin. They are also known to take bites of buoys, paddle boards, brightly colored kayaks, zodiac boats, and other man-made objects floating in the ocean.
"Everyone wants to think sharks just search out seals, but they bite a lot of things that don't resemble any of their known prey," said A. Peter Klimley, an expert in marine animal behavior at the University of California, Davis, and author of the Secret Lives of Sharks and co-author of Great White Sharks: The Biology of Carcharodon carcharias. "They don't tear these things to pieces. They take a bite, feel them over, then move on."
The Taste Test
If sharks bite to figure out the nature of various objects, then why do they usually spit out people rather than adding them to the menu?
"They spit us out because we're too bony," said Martin.
Great whites have extremely slow digestive tracts; if they eat something less than optimal, it slows down their digestive tract for days, prohibiting them from eating other things. "That makes them selective about what they eat," said Klimley.
The insulation that keeps seals warm is pure fat, which provides twice the calories of muscle. That makes them a favorite of great whites. A high fat diet is mandatory for the great white to maintain its body temperature and keep its brain warm in cold water.
Still, sharks do attack people along U.S. coasts and around the world, even if the nature and number of encounters belie expectations.
There are steps society can take to reduce the number of incidents.
Cities often use beaches as burial grounds for marine mammals that wash up dead—like beached whales. "There is a possibility that when those animals are buried, some of the decaying material washes out to sea and attracts sharks," said Collier.
A healthy avoidance of pinniped colonies is another way to minimize human fatalities. A more subtle point is to steer clear of river mouths dumping spawning fish into the sea. Fish runs attract pinnipeds, which attract great whites. They feast on both seals and salmon, also a favorite shark snack.
"What we need to remember is that if great whites really liked to eat people, there would be a lot more fatalities," said Collier. "And I wouldn't interview so many survivors."
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As far as I know, this definition of intelligence is original with me.
And although it may seem a fairly good attempt to define a complex and
subtle concept in theory, it is extremely difficult to apply in practice.
For example, not all decisions are of a simple either-or type; some are
mind-bogglingly complex, involving the careful weighing of many factors and
options before a decision likely to yield 'desirable' results can be
reached. Therefore, comparing the number of units of time it takes an animal
to arrive at decisions of different complexity - even assuming we can
understand all of the parameters, sub-decisions, and implications involved -
is all but meaningless. Further, it is extremely difficult to trace the
reproductive consequences of a wild animal's decisions. While it is fairly
easy to trace human descendants and captive animals from virtually any pair
of biological parents, this is much, much harder to do in the wild. It is
conceivable that, sometime in the future, it may be possible to model all
decisions as a series of binary options and to track the genetic legacy of
any wild animal parent. But until such methodologies become available, my
definition is not terribly helpful toward measuring the intelligence of the
White Shark. 