Science / Medicine : Great White Lies? : Maybe the mammoth shark isn’t a super predator after all. One researcher theorizes that many people escape from attacks because the shark is afraid of injury and adopts a hit-and-run approach.
Biologist John E. McCosker still remembers the chilling day in 1980 when he got his first close-up look at a great white shark in a feeding frenzy.
He was in a steel observer’s cage, suspended off the side of a boat at Dangerous Reef, along the shark-ridden southern Australia coast. “I’m a little foolhardy, but not a fool,” he says. Still, he was near enough to the 12-foot-long beast to notice something very strange about it.
As it raised its snout, opened its cavernous jaws and struck at the bait--a chunk of horse meat that McCosker and his Australian colleagues had set out for it--the shark rolled back its eyes, almost as if to protect them.
That was very puzzling behavior in an animal with no reason to fear anything, other perhaps than a well-equipped fisherman, though at the time McCosker didn’t give it much thought.
Now, after many years of studying Carcharodon carcharias --the great white shark--he has become convinced that the strange eye-roll could explain one of the lingering mysteries about the legendary predator: Why so many people manage to survive its attacks.
McCosker’s observations, detailed in his new book with co-author Richard Ellis, “Great White Shark” (Harper Collins), cast considerable doubt on the great white’s image as the ultimate predator. Rather, it seems to be a prudent “mugger,” attacking gingerly to make sure it is not injured in the fight.
In recent years, the number of attacks on humans by the sharks has increased significantly, especially on surfers and divers in the waters off Northern California. The area is called the Blood Triangle and the Great White Shark Attack Capital of the World. Yet for all their ferocity, the sharks usually release their victims after only a single bite. Of the 60 or so attacks in the past half-century off California, only six have been fatal.
To McCosker, director of the California Academy of Sciences’ Steinhart Aquarium here, this “bite-and-spit” behavior seemed paradoxical. As he puts it, “Is the great white such an ineffectual predator that nine out of 10 of its victims escape to tell about it?”
One explanation offered by biologists is that great whites don’t really like the taste of people. But McCosker, who tracks attacks by great whites along the California coast and once even displayed a young one at his aquarium, didn’t buy it.
Explaining why, McCosker, 45, warms to his subject with characteristic enthusiasm, imagining himself in the mind of the shark. “Does it bite down on its prey, then, finding the flesh distasteful, say to itself, ‘Phooey, I thought that was a seal,’ and release it?” he asks, feigning a look of disgust. “Well, the answer is that great whites have certainly eaten people.”
Nor does he think much of variations of what he calls this “doesn’t taste good” theory. “Some people say it’s the neoprene of a diver’s wet suit. Or that it’s the fiberglass of the surfboard. Or even the suntan lotion we might be wearing,” McCosker says. But, he points out, such ideas are totally at odds with what is known about the shark’s eating habits.
“When you look into a white shark’s stomach, you find tin cans, rubberized material, all sorts of strange things,” he says. “That certainly tells you taste isn’t important to them. They’re indiscriminate scavengers.”
What’s more, he says, when they’re all riled up by blood and flesh, as was the shark outside McCosker’s cage in Australia, they’ll attack just about anything, including the steel bars of the enclosure. “We’ve even found logs floating with white shark teeth in them,” he says.
So what is it that’s happening when a shark attacks a human, then inexplicably releases its victim when it could just as easily gobble it up?
McCosker says the answer came to him while he was making one of his frequent forays to the Farallon Islands, 26 miles off San Francisco’s Golden Gate. Uninhabited except for a few research biologists, these rocky heaps teem with wildlife, including various species of seals and sea lions, favorite foods of the great white.
During the elephant seal’s winter birthing season, scientists have counted an average of an attack a day by great whites on seal pups in the surrounding waters. Yet like humans, many of the pinnipeds survive the harrowing experience by scampering off after the shark’s initial bite and beaching themselves.
Discussing these attacks with McCosker, Harriet Huber, an ornithologist then working with the Point Reyes Bird Observatory on the Farallons, vividly described a typical attack. She told how the great white surprises the seal, usually while it is swimming on the surface, takes a bite out of it, then spits it out. But it doesn’t abandon its wounded prey. Instead, it continues to lurk at the scene, circling its victim while it weakens or dies from the loss of blood. Then if the seal hasn’t made it to shore, it comes in to finish it off.
McCosker knew from his own experience with seals that there was good reason for the shark’s hesitation. Seals are equipped with formidable claws--some longer than human fingers--and if they are threatened, they don’t hesitate to use them. “You don’t want to mess with a mad seal, particularly an injured one,” McCosker says.
He also knew that great whites really have only one vulnerable spot: their large black eyes. Lacking a covering membrane, they are an easy target for an enraged seal. McCosker himself had seen what appeared to be healed claw marks on the snouts of great whites in Australia. He also recalled the strange movement of the shark’s eyes at the moment of attack. By rotating them so completely in their sockets that the lenses were no longer exposed, he speculated, the shark could well be shielding them from sharp, dangerous objects, like seals’ claws.
As these clues came together during his visit to the Farallons, everything finally became clear to him. Says McCosker: “I said to myself, ‘Wait a minute, you dope, why are we trying so hard to create a special case for humans, when in fact for tens of millions of years white sharks have been attacking pinnipeds in the exact same way?’ ”
There was no reason, McCosker realized, for the sharks to treat humans any differently than their traditional prey. “It wouldn’t make evolutionary sense,” he says.
If there is any lesson from this new insight into shark behavior, McCosker says, it is that humans can take advantage of this lull after the initial attack, especially if they make sure they are not alone when entering water known to have great white sharks.
In California, where divers and surfers usually adhere to the buddy system, McCosker says, attack victims stand a good chance of surviving because there is a companion around to help them ashore or to the safety of a boat after the initial bite. But if there is no one else present to provide assistance, the shark will soon move in for the kill. As proof, McCosker cites a cluster of four shark attacks in Chile, where solo diving is much more common. There was only one survivor, a swimmer who had gone out with a buddy.
McCosker concedes that his views challenge the popular image of the great white shark as some kind of super predator--”that it can eat anything in front of it,” as he puts it. But that is absolutely wrong, he insists. Rather, the great white is more of a sneaky, hit-and-run attacker that will not take on anything directly unless it is sure it will not be injured.
With its great size (14 feet or longer), an adult great white, unlike a seal, is not very agile. Large and lumbering, it has to surprise its prey, striking from the rear and below. “It’s really a mugger,” McCosker says. “It doesn’t attempt to inhale its victim because that’s more than it can easily do. Rather, it immobilizes it to protect itself from any sharp, quick claws that might imperil its eyes.”
For these reasons, the great white shark has developed what McCosker calls “a prudent strategy of bite, spit and wait, often just lurking at the periphery after a strike, watching the hapless victim bleed before charging in to feed.”
