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White Sharrk Attack! Fact And Fiction

Text by Dr. Erich Ritter, Chief Scientist
Global Shark Attack File, Shark Research Institute, Princeton, New Jersey, USA

 

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Great White Shark
Great White Shark, Carcharodon carcharias, Australia, Pacific Ocean Image #: 009533

Fact or Fiction? Fiction is most likely the answer when it comes to this great animal, Carcharodon carcharias--the white shark. It is the most featured animal where descriptions don’t match the truth. No other animal has so tightly captured our fascination and imagination over decades like this super predator: a perfect model of speed, power and hunting skills. Because of its overwhelming features, white sharks trigger fantasies that hardly fit the real profile of this amazing hunter. Not too long ago, beaches emptied within seconds when a shark was spotted, creating a hysteria unknown for any other animal—a hysteria created by fiction and fueled by erroneous media reports. And the white shark took all the heat. If one thing is true about this animal it is that the written and spoken word is mostly wrong. They are no more dangerous than any other large animal that encounters humans. They are not sneaky, unpredictable or bloodthirsty, and, certainly, not cold killers—they are simply not yet understood. It is hard to convince the public that white sharks have been truly misjudged and misinterpreted when most scientists share the public’s opinion. This has to change if we want to save the white shark. If we lose this species, we do not just eliminate one of the most amazing success stories of vertebrate evolution; it proves we are incompetent of running our planet.

Scientists have only started to scratch the surface on some topics and many aspects of white shark biology are still unknown. It is still a mystery where their breeding grounds are, how many pups they have, what their length at birth is, and when they reach sexual maturity. Not even their origin is clear. It seems to be solidly established that the first white sharks appeared about 6 million years ago, but who where their ancestors? How do they feed? How do they hunt?

White sharks are true apex predators and as such have a key function in the marine ecosystem. Contrary to general thought, they are not indiscriminate eaters who bite and eat everything that crosses their path – even though they are at the top of the food chain. Many aspects of their feeding biology are still unknown, but it is clear they are specific feeders. Young white sharks don’t possess the stereotypical triangular teeth but rather long slender ones to catch fish. Once they get closer to maturity, their teeth change to the well-known shape, making it possible for them to catch seals, or feed on other large prey. Nevertheless, even as adults they feed to a great extent on fishes.

White sharks primarily feed on live prey but also scavenge as well, mainly on whale carcasses. Theories have it that large white sharks feed once a week or even less and consequently focus on energy rich sources. Yet white sharks show a wide distribution and many areas do not offer large prey in abundance, so these sharks feed much more often. White sharks mainly live in cold and temperate waters but can also be found in subtropical areas during winter months. Although they have been fished in deep waters, they prefer the coastal shallow water, with a temperature of less than 15° Celsius. White sharks and other members of this family possess a unique physiological system to enhance their body temperature, which can be held constantly between and 10 and 15° Celsius above ambient water temperature. Such an elevation of body temperature enables the muscles of these animals to contract faster and hence allows them to be more agile, a necessity if catching swift prey in cold water.

Knowledge of hunting strategies is scarce and based largely on surface observations or carcass analysis, techniques that leave many questions unanswered. Recently, the breaching phenomenon has shed more light on hunting strategies, though the initial interpretations seem rather wrong. Photographers started to pull decoys of various shapes and sizes behind boats to trigger breaching in white sharks. Breaching was first interpreted as the way they normally would attack and catch seals. However, my investigations suggest that sharks do not mistake the decoys for seals and try to kill them. Rather, they use them for target practice, often releasing the decoy while still airborne, leaving only slight scratches on its surface. White sharks do not "blindly" attack the object, and despite their power and speed, are capable of coordinating a high speed approach and investigation at the same time. In addition to the actual act of grabbing the decoy, the time before the bite offers insight as well. The shark does not always approach the decoy in the stereotypic "below and behind" manner. White sharks have been seen jumping into the moving direction of the decoy. This "reverse approach" creates an interpretation problem considering the visibility is often less than distances needed to reach the breach speed when the decoy gets into sight. One way or the other, what scientists initially interpreted as an obviously overpowering way of catching prey appears to be a much more complex behavior that is challenging to fully understand.

Another challenging research question concerns the vision of white sharks and their capability of shape discrimination. The well known "mistaken identity" theory comes to mind in connection with attacks on surfers. But does a white shark really confuse a surfer for a seal? No one can answer that conclusively, but more and more evidence speaks against this idea. For myself, having worked with white sharks for years and having seen many times how they approach a known and unknown object, investigate the situation, and kill a prey, there is no doubt in my mind that these animals know with certainty that a surfer is not a seal. White sharks check out unknown things because of possible palatability and hence selective advantage over other white sharks. I have studied approach behaviors in white sharks extensively and found different patterns that can lead to a surfboard bite. One distinctive behavioral pattern consists of exploratory behavior where white sharks, and other species as well, examine new objects by grabbing them. But to approach unfamiliar objects and even bite them is potentially dangerous for an animal, confirming why shark bites on surfboards are so rare. If "mistaken identity" were true, beaches all over the world would be covered with uniquely shaped boards on a regular basis. Over the years I have examined many cases of surfers who have been bitten due to this kind of behavior and the bite pattern was always very distinctive, and different from bites on seals. Nevertheless I designed a series of hands-on experiments to test whether what I postulate is true.

My research group and I mimicked seals by wearing black dive suits and free dived with them without protection to trigger reactions in the line of the mistaken identity. The outcome speaks for itself—we are all intact. White sharks are capable of making a clear distinction between known objects and us, independent of whether we sit on a board, float on the surface, ride the wave, or dive down. And it does not matter if one wears black or not. Overall color does not seem to lead to an increase of attack. It is often heard that bright colors attract sharks and as such increase the rate of bites, and the most attractive of them is yellow, often referred to as "yum-yum yellow." This theory originated in the early days of shark research when scientists looked for potential triggers for attacks. No one ever did conclusive research on color preferences, but nevertheless this "fact" made it into the books. Super predators of all kinds have a "built in" mechanism that causes them be very hesitant when they encounter an unknown object of large size, since it could potentially be dangerous. Our experiments are not conclusive yet, but we are far beyond the level of an "exception to the rule" that sharks mistake a surfer or a free diver wearing black for a seal. Besides mistaken identity or color as a reason to attack, many other assumptions about sharks have never been tested, but still make it into the books as "facts" a major impediment to establishing valid theories concerning attack behavior.

What’s next? The most important step is to make white shark behavior understandable to the general public. Humans prefer to destroy anything they do not understand and perceive as harmful. White sharks may be on the brink of extinction and worldwide protection is necessary. "Protection through education" is key. One useful tool is to interact with these animals and prove that by following certain rules even these animals can be approached without being attacked. This would be a giant leap towards protection of white sharks and would help all shark species that suffer from bad reputations given to them over decades out of human fear, misunderstanding and pure ignorance. People have been safely interacting with white sharks for a while now without the safety of a cage. Nonetheless, scientific analyses and approaches are needed. One important part is to understand signaling. What does it mean when a shark performs certain signals, how does one react, and how does one test them? Another important part is to understand what went wrong when a shark bit a human. Reconstructing shark accident scenarios is a valuable and essential instrument to understand behavior. To know what angers a shark in general or white shark in particular and to recognize the signal prior to an incident will go a long way towards enabling humans to safely share the water with these large predators that were feeding in the ocean for eons before our kind first set foot in it.