Sharks 101

True or False: All sharks are dangerous.

• True

• False

Answer explanation

Of the world's roughly 400 shark species, 80% are unable to hurt people or rarely encounter people. The shark species that are responsible for most attacks on humans are great white, tiger, and bull sharks.

True or False: Most people attacked by sharks are killed.

• True

• False

Answer explanation

Of every 100 people attacked by sharks, 85 survive. Many large sharks commonly attack by biting their prey to immobilize it before trying to eat it. Consequently, many potential prey escape and survive. Most shark encounters with humans appear to be investigative, not predatory.

True or False: Sharks are not found in freshwater.

• True

• False

Answer explanation

A specialized osmoregulatory system enables some species (such as bull sharks) to cope with dramatic changes in salinity, from the high salinity of seawater to the low salinity of freshwater rivers and lakes. For example, bull sharks have been seen as far up the Mississippi River as Illinois and also in Lake Michigan.

True or False: All sharks need to swim constantly.

• True

• False

Answer explanation

Some sharks can remain at rest for long periods on the bottom and obtain enough oxygen by opening and closing their mouths to pump water across their gills.

True or False: Sharks have poor vision.

• True

• False

Answer explanation

The lens of a shark's eye is up to seven times more powerful than that of a human's Sharks can even distinguish color.

True or False: Sharks are voracious eaters that must eat continuously.

• True

• False

Answer explanation

Like other large animals, sharks eat periodically, depending on their metabolism and the availability of food. Humans are not the primary food source of any shark, and many large sharks prefer the higher fat content of seals and sea lions.

True or False: The great white shark is a common, abundant species found off most beaches.

• True

• False

Answer explanation

Great white sharks are relatively uncommon predators that prefer cooler water. At most beaches, great whites are rarely encountered.