No, sharks won’t die if they stop swimming. And when they bite you, they mean it.

A rash of shark at­tacks this sum­mer, in­clud­ing eight in North Carolina alone, has put the gi­ant fish in the spotlight — not that the great white or ham­mer­head needed the pub­lic­ity. Pop cul­ture, medicine and the media have long been fas­ci­nated with sharks,

The Washington Post Sunday - - OUTLOOK - By Xav Judd xavjudd@google­ Xav Judd is a free­lance jour­nal­ist based in Lon­don.

1 Sharks pose a se­ri­ous threat to hu­mans.

Shark at­tacks of­ten mean a media feed­ing frenzy: Cov­er­age in­cludes shots of bloody vic­tims, pic­tures of great whites with gap­ing jaws and il­log­i­cal de­scrip­tions such as “shark-in­fested wa­ters.” (Sharks live in the oceans. They are not an in­fes­ta­tion.) Af­ter an at­tack in North Carolina this sum­mer, au­dio of a 911 call from a dis­tressed by­stander say­ing, “It looks like her en­tire hand is gone” was all over the In­ter­net.

With such treat­ment, no won­der sharks are one of the most feared an­i­mals in the world. But shark at­tacks are ac­tu­ally quite rare. There are al­most 400 shark species, and only about a dozen have ever com­mit­ted doc­u­mented at­tacks on hu­mans. Ac­cord­ing to the In­ter­na­tional Shark At­tack File at the Florida Mu­seum of Nat­u­ral History, only 70 at­tacks oc­curred on av­er­age each year in the past decade, with a hand­ful per year prov­ing fa­tal. Recorded at­tacks have risen sig­nif­i­cantly since the 1960s— by 200 per­cent— though that’s mostly at­trib­ut­able to an in­crease in peo­ple swimming in the sea for leisure and to bet­ter gath­er­ing of data.

The risk of a shark at­tack while you’re in the wa­ter is in­finites­i­mally small: about 11.5 mil­lion to 1. Hu­mans are more likely to have deadly en­coun­ters with lions (which kill about 100 of us yearly), crocodiles (around 1,000) or snakes (close to 50,000). You’re 10 times more likely to be bit­ten by another hu­man in New York City than you are by a shark any­where on the planet.

The threat, in fact, is the other way around: The World Wildlife Fund es­ti­mates that peo­ple slaugh­ter about 100 mil­lion sharks per year. They’re caught com­mer­cially for their liver oil, meat and fins, or they die be­cause of sport fish­ing, drum lines (aquatic traps from which sharks usu­ally don’t emerge alive) and beach pro­tec­tion net­ting. These an­i­mals take sev­eral years to ma­ture and of­ten pro­duce few young; many species face ex­tinc­tion.

2 Sharks have to keep swimming.

It’s been re­peated by sources both au­thor­i­ta­tive (text­books) and slightly less so (Ri­p­ley’s Be­lieve It or Not!): Sharks must move con­stantly in or­der to breathe, or they die.

But for most species, that’s not true. Sharks em­ploy two meth­ods to breathe. Ram ven­ti­la­tion en­tails swimming con­stantly, which forces wa­ter over the gills. Buc­cal pump­ing uses mus­cles in the mouth to pull liq­uid over the gills. Fish in this lat­ter group, in­clud­ing an­gel and nurse sharks, don’t need per­pet­ual mo­tion and can rest on the seafloor. Many shark species can use both tech­niques. About 20 species can’t, though even they won’t nec­es­sar­ily die if they stop swimming. Re­searchers have dis­cov­ered that some of these an­i­mals can re­main rel­a­tively sta­tion­ary: In 1972, Caribbean reef sharks were ob­served at rest in a Mex­i­can cave.

3 Sharks don’t get can­cer. no­tion

Wil­liam Lane’s 1992 best­seller, “Sharks Don’t Get Can­cer: How Shark Car­ti­lage Could Save Your Life,” helped pop­u­lar­ize the myth­i­cal of sharks’ in­vin­ci­bil­ity. The book seemed at least par­tially grounded in re­al­ity: Re­search from the pre­vi­ous decade sug­gested that in­sert­ing shark car­ti­lage into cer­tain an­i­mals in­hib­ited the growth of blood ves­sels that nour­ish tu­mors, and that sharks had lower in­ci­dences of can­cer than hu­mans did. Lane’s book ac­knowl­edged that sharks oc­ca­sion­ally get can­cer, just not of­ten. But it was the mis­lead­ing ti­tle that res­onated.

It’s been known since 1908 that sharks get can­cer; that was when the first in­ci­dence of a ma­lig­nant growth was dis­cov­ered in a spec­i­men. More re­cently, a com­pre­hen­sive 2004 study found 42 car­ci­no­mas in Chon­drichthyes species, the class of car­ti­lagi­nous fish that en­com­passes sharks, skates and rays. To date, can­cer has been doc­u­mented in 23 species of sharks.

No sci­en­tific ev­i­dence shows that car­ti­lage from these an­i­mals can pre­vent us from get­ting can­cer or cure it, as Lane ar­gued. In 2005, the Na­tional Cen­ter for Com­ple­men­tary and Al­ter­na­tive Medicine gave a brand of car­ti­lage called BeneFin to pa­tients who had ad­vanced bowel or breast can­cer. There were no pos­i­tive ef­fects.

Yet Lane made hand­some prof­its through his com­pany, LaneLabs, selling shark car­ti­lage ex­tracts to ease rheuma­toid arthri­tis, pso­ri­a­sis and di­a­betic retinopa­thy, an eye con­di­tion. The glob­al­mar­ket for such prod­ucts was thought to have ex­ceeded $30 mil­lion by 1995. In1999, the Food and Drug Ad­min­is­tra­tion sued LaneLabs to pre­vent the com­pany from mar­ket­ing shark car­ti­lage as an­ef­fec­tive can­cer treat­ment. Lane later agreed to pay a $1 mil­lion set­tle­ment.

4 Aerial pa­trols keep peo­ple safe from sharks.

A string of shark sight­ings and at­tacks in the past few years has prompted a num­ber of Aus­tralian states to in­crease aerial pa­trols, manned air­craft that mon­i­tor recre­ational wa­ters for sharks. But af­ter decades of op­er­a­tion along the coast there, there’s lit­tle ev­i­dence to sug­gest that this has any prac­ti­cal ben­e­fit in keep­ing swim­mers safe.

Air­planes or he­li­copters have to sur­vey a vast area in just a few hours. Some species, in­clud­ing the great white, are am­bush hun­ters and come up to the sur­face only when they strike. Oth­ers lie deeper in the ocean; if the wa­ter is murky or the skies not clear, they can be al­most un­de­tectable.

A smarter way to en­sure beach­go­ers’ safety is a “shark bar­rier,” cur­rently used in parts of Aus­tralia and Hong Kong. These thin mesh nets — which aren’t harm­ful to wildlife and shouldn’t be con­fused with shark nets — form an un­der­wa­ter fence from seabed to sur­face around beaches and keep preda­tors out.

5 A shark at­tack is a case of “mis­taken iden­tity.”

Af­ter an at­tack, media out­lets of­ten quote ex­perts who say the shark mis­took the hu­man for some­thing else; author­i­ties in­clud­ing the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion re­it­er­ate that at­tacks on peo­ple are “usu­ally a case of mis­taken iden­tity.”

But plenty of ev­i­dence sug­gests that shark at­tacks on hu­mans, though rare, are in­ten­tional. Some­times sim­ple cu­rios­ity prompts a bite. A shark might also at­tack hu­mans if they’re in its ter­ri­tory or if it sees them as com­pe­ti­tion for food.

Some species have highly re­fined senses, and these re­mark­able hun­ters know ex­actly what kind of an­i­mal they are pur­su­ing. These species will prey upon peo­ple. The tiger shark, nick­named the “dust­bin of the seas,” will eat prac­ti­cally any­thing— re­mains of horses, dogs, li­cense plates, tires and peo­ple have been found in their stom­achs. Bull sharks have been im­pli­cated in many hu­man fa­tal­i­ties. And the oceanic whitetip, which oceanog­ra­pher Jac­ques Cousteau de­scribed as “the most dan­ger­ous of all sharks,” has been known to tar­get shipwreck and plane-crash sur­vivors.



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