Species • There are over 360 species of sharks! • They can range in size from small enough to fit in your hand to up to 46 feet!! • Smallest Shark is the Pygmy Shark • Largest Shark is the Whale Shark – Filter feeder, feeds on plankton Skeleton • Sharks are cartilaginous fish • Skeleton made of cartilage which is lighter and more flexible than bones Respiration • Sharks have uncovered gills used for respiration • Extract oxygen as water passes over the gills • Most species of shark can pump water over their gills for when they are not moving using the spiracle • A small percentage of sharks need to stay in constant motion to respire Teeth • Sharks teeth are NOT attached to their jaws • Teeth range from needlelike to large flat teeth • Teeth are grown and replaced often • Sharks have multiple rows of teeth • Sharks can have about 25,000 to 30,000 teeth in one lifetime • Some replace teeth every 8-10 days, others every few months Life Span • Lifespan varies by species • Most live about 20 – 30 years • The spiny dogfish can live up to 100 years • It is thought that the whale shark can live over 100 years as well Sense of Smell • Incredible sense of smell • They can detect amounts of blood as small as 1 ppm. (part per million) • Rely on sense of smell to locate prey Locating Prey Lateral lines Electro-receptors Sense organ used to Allow sharks to detect motion or sense minute vibrations in the electricity caused water by muscles and nerves in prey Vision • Sharks have eyelids but do not blink • Water surrounding eye cleans it • Sharks have a membrane over eye that protects when being attacked or during predation • Great White Sharks roll eyes back when attacking Do Sharks Sleep?? • Scientists unsure!! • Possible they sleep in a similar manner to Dolphins – Half the brain sleeps at a time Shark Attacks • 2000 - 79 attacks, 11 fatalities • 2005 - 61 attacks, 4 fatalities • 2006 - 62 attacks, 4 fatalities • Majority occur in the United States • More people die from lightning strikes each year Sharks Involved • Three types of sharks have been involved in a significant amount of attacks – Great White – Tiger Shark – Bull Shark Great White Shark • Great Whites are generally about 13-16 ft and weigh 1500 - 2450 lbs • Found in waters between 54 and 75 degrees F • Countershading – White underside and gray dorsal side – Difficult to see when looking at horizontally – When seen from above, gray blends in with the water – When seen from below, white blends in with surface of water Typical Prey • Sting rays, tuna, smaller sharks, dolphins, seals, sea lions • Shark attacks most often occur in the morning, within 2 hours after sunrise • Hard to see a shark close to the bottom • Attack from below at fast speeds Tiger Sharks • Average 11 feet and 850 - 2000 lbs • Commonly found around islands in the central Pacific • Dark spots and stripes are prominent in young sharks and fade as the shark matures Hunting Habits • Teeth can bite through bone and turtle shells • Known to circle its prey and even study it by prodding it with its snout • Tiger sharks devour their entire prey when attacking Hawaii • Tiger sharks have become a problem in Hawaii • Hunted to help control attacks, but no decrease occurred • Considered sacred by native Hawaiians Bull Shark • Dwell in shallow water, possibly posing highest threat to humans • Can tolerate freshwater • Males: 6.8 ft, about 200 lbs • Females: 11.5 ft, about 700 lbs Hunting Habits • Bump and Bite Technique • Shark circles prey often bumping them before the actual attack. • They are extremely territorial and will attack other animals that enter their territory. Why attack? • Mistaken Identity: – Shark mistakes a person in the water as a seal when looking from below the waters surface • Curiosity • Sharks typically bite once and then swim away • Explanations: – Humans do not taste like their typical prey – Return to the prey after it exhausts itself Dolphin Protection • Sharks will not attack when dolphins are around • Scientists unsure why this phenomenon occurs Avoiding an Attack • Avoid water during darkness or twilight hours • Do not enter water if bleeding from an open wound • Do not wear shiny jewelry – resembles fish scales • Avoid areas near commercial fishing • Avoid murky waters • Do not splash a lot Fending off an attack • Hit back in sensitive areas such as the eyes and gills • Shows shark you are not defenseless Hammerhead Shark • Habitat: Shallow tropical and warm temperature waters • Diet: Stingrays, Other small sharks, fish, crustaceans • Size: 12 - 20 ft. • Attacks: 18 (0 fatal) • Hammerheads have small mouths and seem to do a lot of bottom-hunting. (Stingrays!) • Their wide-set eyes give them a better visual range than most other sharks. • They are also known to form schools during the day, sometimes in groups of over 100.
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