Patterns of White Shark Attacks
In an age rife with modern-day perils, shark attack remains an ancient and fearsome possibility. The horrifying prospect of being torn asunder and eaten by a swift, razor-toothed wild animal in an environment where we cannot see, breathe, call for help, or escape taps into our deepest, darkest, and most atavistic fears. That one person is stricken while another is not lends a frightening unpredictability to the phenomenon. One's control over his or her fate evaporates at the water's edge. Anyone in the ocean at any time may be ripped to shreds by an unreasoning alien 'monster' – even you or someone you love. It is exceedingly difficult to think clearly and rationally about something so overwhelmingly terrifying and potentially so acutely 'personal'. But think clearly and rationally we must if we are to understand why some sharks – including the Great White – sometimes attack humans.
Australian surgeon Victor Coppleson was among the first modern scientists to attempt to understand and explain why sharks occasionally attack humans. In a highly influential book published in 1962, Coppleson collected and analyzed 281 accounts from Australia and around the globe of shark attacks on swimmers, surfers, skin divers, and shipwreck survivors. Coppleson became convinced that sharks do not attack humans in water cooler than 70° Fahrenheit (21° Celsius) and that each cluster of attacks that occurred in the same general area – even those separated by many years – were committed by a single shark. Based on this notion, he proposed that – like the notorious tigers, lions, and crocodiles of terrestrial folklore – some sharks, possibly infirm or ill, became habitual man-eaters. These so-called "rogue sharks", Coppleson suggested, developed a taste for humans as easy prey. Many of Coppleson's conclusions did not stand up to later research. Data compiled by other researchers made it clear that shark attacks do, in fact, occur in waters significantly cooler than 70°F (21°C). For example, in July 1936 Joseph Troy was fatally attacked by a shark – believed to have been a Great White – in Buzzards Bay, Massachusetts; even allowing for the shoreward shift of the Gulf Stream in summer, the water temperature at the time was probably no more than 59°F (15°C). Later data also thoroughly discredited the rogue shark theory as a viable 'explanation' for the majority of shark attacks, whether clustered or not. But some sharks do grow old and others occasionally become wounded or ill.
In February 1966, Raymond Short was attacked by an 8-foot (2.5-metre) White Shark at Coledale Beach, near Sydney, Australia. Rescuers removed Short from the water with his attacker still firmly clamped to his right leg. That is unusual enough, but what makes this case particularly intriguing is the shark itself. In a 1967 paper by T.B. Gorman and D.J Dunstan, photographs of the attacking shark clearly show that its abdomen bore recent, massive wounds, apparently inflicted by the bite of a comparably large shark such as a Tiger (Galeocerdo cuvier) or Bull (Carcharhinus leucas) Shark. The attack occurred in a very unusual habitat for a White Shark: the water was 5 feet (1.5 metres) deep and very murky. The attacking shark was an immature female about 5 years old. At that growth stage, a White Shark off southeastern Australia would almost certainly have moved far from the shallow nursery area where it was born, has no reason to come inshore to breed, ordinarily inhabits relatively clear water more than 20 feet (6 metres) deep, and feeds on teleosts, crustaceans, smaller sharks and rays. From the photographs in Gorman and Dunstan, the young White Shark appears to be somewhat emaciated, its skin shriveled and wrinkled. Could the shark that attacked Raymond Short have been too weak to capture its normal prey? To free Short, the shark's jaws had to be prized open on the beach. Did it refuse to let go – even as it was being removed from the water – because it was desperately hungry or because, in its starved condition, its jaw-opening muscles were physiologically sluggish or recalcitrant? We will probably never know for sure, but it is tempting to conclude that the White Shark that bit Raymond Short attacked out of a desperate need for food, any food – even something as large and unfamiliar as a clumsy-swimming primate.
In a pivotal 1963 paper, South African zoologist David Davies collected and analyzed 58 case histories of shark attacks from Natal, the Cape Province, and Mozambique. Davies compared the frequency of shark attack to such factors as sea temperature, beach patronage, and seasonal abundance of supposedly dangerous sharks. He found that beach patronage was highest when the water was warmest and that there was a strong correlation between beach patronage and incidence of shark attack. This is hardly surprising: high water temperature coincides with high air temperature, compelling a greater number of people to enter the sea to seek refuge from the heat; the greater the number of people in the sea, the more shark attacks will occur. Davies also found that, of the 11 species of sharks caught in the mesh nets set to protect South African bathing beaches, the greatest frequency of attacks coincided well with the maximum abundance of only one species: the Zambezi Shark (once thought to be a distinct species, but now known to be a synonym of the Bull Shark). Davies also concluded that the White Shark is rare on the Natal coast and there was no evidence that this species had ever attacked humans in the area. Unfortunately, Davies had misidentified the species of attacking shark as a Zambezi in at least one case: that of Petrus Sithole, who was fatally bitten in December 1960 at Margate Beach, on the south Natal Coast. Yet, on the basis of Davies' photo of tooth fragments removed from the victim's wounds, it was very probably a White Shark that was actually the culprit. Clearly, unraveling the mystery of when, where, how, and why sharks attack humans and which species are responsible requires drawing on many realms of expertise.
World War II revealed that the putative 'Shark Chaser' chemical repellent dissipated too quickly to provide adequate protection for military personal downed at sea. Spurred by a desire for a truly effective shark repellent to protect servicemen who must work or may find themselves adrift in the ocean, the US Office of Naval Research instigated a program dedicated to conducting basic research on sharks. In June 1958, the Shark Research Panel was formed. The Panel included chairman Perry Gilbert, ichthyologist Leonard Schultz, shark fisheries biologist Stewart Springer, and – later – marine biologist Albert Tester and biochemist/Naval officer H. David Baldridge. Gilbert conducted pioneering work on shark vision, Schultz sorted out which species were dangerous and which were not, Springer worked on shark life history and participated in much repellency research, Tester worked on olfaction and hearing in sharks, and Baldridge worked on collecting authenticated data on shark attacks. From this last grew the International Shark Attack File (ISAF), which eventually burgeoned to some 1,165 case histories. These case histories consisted largely of clippings from newspaper and wire services from around the globe as well as hundreds of the SAF's own two-page attack reporting form, filled out by attack survivors, witnesses, rescuers, and attending physicians. In 1973, it fell to Baldridge and systems analyst Joy Williams to analyze the ISAF data. A year later, Baldridge published a highly influential non-technical book summarizing these findings with exceptional acumen and clarity.
Much of the ISAF data merely re-confirmed Davies' earlier conclusions that shark attack data often tells us more about patterns of human usage of the ocean that it does about shark behavior: most attacks were on young men in relatively shallow water and occurred at or near the surface, attacks peaked during summer months, after work and on week-ends, and so on. The so-called "Red Triangle", an area off northern California extending from Tomales Point to San Francisco to the Farallon Islands, is notorious for shark attacks. Of all attacks by White Sharks on humans documented throughout the world, over half have occurred along this 120-mile (193-kilometre) stretch of coast. But this probably has more to do with the high population density of the San Francisco Bay area (which includes the nearby and populous Silicon Valley) than it does with ferocity of local White Sharks. Many residents and visitors to the Bay Area are fairly affluent and a high percentage of them are keen participants in such ocean activities as swimming, surfing, sea kayaking, sailboarding, skin and scuba diving. With so many people actively playing in waters inhabited by the White Shark, it is hardly surprising that – every once in a while – an incident occurs. Further, because the Greater San Francisco Bay Area has benefit of a first-rate emergency response network, widespread access to modern telecommunications technology, and serves as a base for numerous major mass media corporations, it is exceedingly unlikely that a shark attack would go unreported. It is therefore not surprising that we have more complete shark attack data from northern California than we do from, say, southern Kuwait, northern Kenya, or Kwajalein Atoll.
Yet some surprising facts were revealed by Baldridge's analysis. Perhaps most astonishing was that some 96% of attack victims were struck only once – often bumped with the snout or slashed with the upper jaw teeth, with little or no attempt by the shark to bite or remove flesh. This suggested to Baldridge that, in the vast majority of cases, feeding was probably not the motivation for shark attacks. It was a revelation that has profoundly affected shark attack research ever since. But if attacking sharks were not feeding, what were they doing? In 1969, Baldridge and Williams published a short but provocative paper that suggested many shark attacks seem to be defensive in nature – the attacking sharks were not feeding, but fighting. In a classic 1973 paper, Richard Johnson and Donald Nelson studied the agonistic (threat) display of the Grey Reef Shark (Carcharhinus amblrhynchos). When persistently pursued, this species consistently warned of its readiness to attack via a distinctive, hunch-backed swimming posture. A similar, though subtler, back-hunching behavior was reported by Robin Buckley, who was subsequently attacked by a 16- to 20-foot (5- to 6-metre) White Shark while spearfishing off the Farallon Islands in December 1975. Could this shark have been threatened by Buckley, or was it merely contesting possession of the speared fish? We will probably never know for certain, but – since even a medium-sized White Shark is much more massive than an average-sized man – the latter motivation* seems more likely than the former.
Identifying the species of shark responsible for a given attack is extremely difficult. In the wild, most lay people – and, truth be told, many marine biologists and ichthyologists – cannot reliably distinguish one free-swimming species from another. For example, a medium-sized Blacktip Shark (Carcharhinus limbatus) very closely resembles a Caribbean Reef Shark (Carcharhinus perezi) of similar dimensions – both are generalized whaler sharks with dusky fin tips – but can be fairly reliably distinguished on the basis of anal fin coloration: unlike the Caribbean Reef Shark, the anal fin of the Blacktip Shark is not black-tipped. In the bloody, mind-stuttering panic and swirling confusion of a shark attack, it would require exceptional knowledge and powers of concentration to look for identifying field characters – especially if it is one's self who has been struck. In Baldridge's analysis, out of 1,165 cases only 257 (22%) cases had benefit of someone who thought they could identify the shark that had attacked the victim. Of those 257 identifications, 32 (12.5%) were White Sharks – more than any other single species. In 1988, after a funding lapse of 20 years, the ISAF was transferred to the Florida Museum of Natural History (FMNH), in Gainesville. The SAF is now operated under the aegis of the American Elasmobranch Society and is curated by ichthyologist George Burgess. According to the FMNH's webpage (as updated August 1997), some 42 species of sharks have been indicted for 882 attacks that occurred throughout the globe between 1554 and 1997. Of these, some 311 (35%) were perpetrated by White Sharks. Clearly, of the 465 or so shark species that roam the seas, the Great White is among the most dangerous.
Since 1960, researcher Ralph Collier has been investigating shark-human interactions, specializing in White Shark attacks on humans. Unlike the ISAF, which relies largely on data supplied by news-media coverage and attack reports submitted sporadically by colleagues, Collier seeks out interviews – often in person or via letters and telephone – with virtually everyone involved, however remotely, with a given attack: survivors, witnesses, rescuers, coast guard, police, paramedics, attending and consulting physicians, coroners and medical examiners, biologists, and anyone else he can contact who might be able to shed some light on what happened. As a result of Collier's patience, persistence, and sensitivity toward victims and their families, his White Shark attack data are exceptionally rich and detailed – often including information, and even entire case histories, that the ISAF does not bother with or know about. (In fact, most of the detailed case history information in this section that is not credited to a specific paper or book is very kindly and generously made available to me by Ralph Collier, drawing on the copious and hard-won data in his personal research files.) In addition, Collier has examined – and often dissected – every White Shark he could from California waters and studied in scrupulous detail films and reports of normal predatory behavior of the White Shark. From his earliest investigations, Collier has carefully studied and recorded wound characteristics, behavior of the victim prior, during, and after an attack, and – most importantly – behavior of the shark before, during, and after an attack. Unlike most of his colleagues, it seems, Collier believed that knowing exactly what an attacking shark did could reveal a great deal about its motivation.
Important New Book on
Important New Book on Shark Attacks!
The culmination of four decades' of research by my friend and colleague Ralph Collier, President of the Shark Research Committee, this book is the first scientific study of every verified shark attack that occurred along the Pacific Coast of North America during the 20th Century. Vivid accounts of attacks by survivors, rescuers, and witnesses are punctuated with chilling, never-before published photos. Patterns in shark attacks are identified, possible motivations for attacks are discussed, and activity-specific safety guidelines for swimmers, divers, surfers, and sea kayakers are offered. The individual case histories are fascinating; the general conclusions and safety guidelines are applicable word-wide. If you are interested in Great Whites or shark attacks, this is a Must Have book.