September 29, 2011

Facts: Deadliest Sharks

  • Out of some 400 species of shark, only three species account for more than 50% of reported shark attacks on humans, the great white shark, the tiger shark and the bull shark. However, most attacks do not result in fatalities, and you are 30 times more likely to be struck by lightning in the US than to be killed by a shark.

  • In order for sharks to breathe, water must move across their gills and therefore they spend their time in constant motion. While scientists do not know precisely how sharks sleep, studies have shown that the mechanism responsible for swimming is located in their spinal cord and not in the brain, so one popular theory is that they are able to shut down sections of their brain like the dolphin while remaining in constant motion.

  • Volusia County, Florida, home to New Smyrna Beach and the Daytona Speedway, has the dubious honor of being called the shark attack capital of the world. Between 1999 and 2008, Volusia County reported more than 21% of the world's shark-human encounters. But here's a piece of good news—0 total fatalities.

  • Though the whale shark is the largest known shark species, it is primarily a plankton eater, leaving the great white to take the crown as the largest predatory shark.

  • The largest shark ever caught on record was a 20-foot (6.1-meter) great white caught off of Canada in 1983.

  • The great white shark has as many as 3000 teeth at one time growing in stacked rows along the upper and lower jaw. Their teeth are not attached to the jaw, like human teeth, and regularly fall out. When one falls out, a new tooth moves into the gap from one of the rows. A shark can lose as many as 2,000 teeth every year!

  • If a great white shark consumes a solid meal of meat and blubber, such as from a whale carcass, scientists have calculated that it would be able to go up to two months without eating again.

  • While the great white is by far the most notorious shark in the ocean to most people, its numbers may be declining. New information indicating that great whites migrate much larger distances than previously thought have revealed that great white population numbers may have been inadvertently inflated for years as a result of double-counting, and that the near-threatened tiger shark may actually outnumber the great white worldwide.

  • Tiger sharks are named for the characteristic dark stripes that cross the dorsal side of their bodies. These markings are most prominent in juveniles, and fade—though remain visible—into adulthood.

  • Tiger sharks are among the least discriminate sharks when it comes to dining. They have a well-earned reputation for consuming anything that comes their way and are sometimes called the garbage cans of the sea.

  • Tiger sharks have unique teeth. They are curved, being blunt at the apex and sharp in the crescent. This allows them to employ their teeth in a sawing motion, allowing them to easily break into the shells of mollusks and sea turtles with ease.

  • Bull sharks are remarkable for their ability to withstand fresh water for prolonged periods of time—up to 6 years—with some specimens being found as far as 2,600 miles inland in the Amazon River. They accomplish this by having a uniquely fine-tuned osmoregulatory system that balances out the salinity of their bodies with the salinity of their surroundings, and kidneys that can work overtime on demand.

  • In terms of human contact, many scientists consider the bull shark the most dangerous shark species, despite being outranked by the tiger and the great white in reported attacks. It's proclivity for hunting in relatively shallow water and ability to enter both freshwater and salt water environments increases it's exposure to humans and therefore increases the risk of encounters.

  • Don't be fooled by a slow moving bull shark—when they want to, they're capable of bursts of speed as fast as 11 miles an hour!

  • Though Jaws solidified the public's fear of the great white, we may be pinning the crimes on the wrong shark. The real life attacks that inspired the book and the film occurred in New Jersey in 1916. A great white was caught only days after the last attack and has been historically touted as the villain, but a bull shark was caught a days later and 3 of the 12 attacks occurred in a tidal river 15 miles from the ocean—a likely spot for a bull, but an unusual haunt for a great white.

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