- Sharks have only an inner ear, which consists of three chambers and an ear stone called an otolith. A shark's inner ear detects sound, acceleration, and gravity.
- Sharks use sound to locate food.
- Sound is often the first sense a shark relies on to detect prey.
- Under water, sound travels faster and farther than on land.
- Sharks are attracted to low frequency pulsed sounds, similar to those wounded or ill prey would emit. Most attractive sounds are in the frequency of 25 to 100 Hz. Some sharks are attracted to sound sources from distances as great as 820 feet.
- Lateral Lines:
- The lateral line system is a series of mucus-filled canals just below the skin of the head and along the sides of the body. The canal is open to the surrounding water through tiny pores.
- Like the ear, the lateral line senses low-frequency vibrations. It functions mainly in distance perception and detecting low-frequency vibrations and directional water flow. Water movement created by turbulence, currents, or vibrations displaces the canal mucus. The lateral lines in the shark transforms underwater sound or mechanical disturbance into nerve impulses.
- Ampullae of Lorenzini:
- Sharks can also detect electricity, which is emitted in small amounts by every living animal. Sharks may be more sensitive to electric fields than any other animal. Sharks have a special network of jelly-filled canals in their head called the Ampullae of Lorenzini that detect electric fields. This lets the shark pick up weak electrical stimuli from the muscle contractions of animals. It may also serve to detect magnetic fields which some sharks may use in navigation.
- Sharks have good eyesight and they have color vision.
- Shark eyes have a large, spherical lens, a cornea, a retina, an iris, and a pupil. They even have good vision in dim light.
- Sharks, like cats who also see well in dim light, have a mirror-like layer in the back of the eye, the tapetum lucidum. This layer doubles the intensity of incoming light, enhancing light sensitivity.
- Unlike other fish, shark's pupils can dilate and contract to control the amount of incoming light. The retina has a greater proportion of light intensity sensors (rods), than color
sensors (cones), so sharks are very sensitive to small differences in light intensity (dark versus light).
- Some sharks have a nictitating membrane, a type of second eyelid, that protects the eye during hunting.
- Sharks that live deeper in the oceans usually have larger eyes than those that live nearer the surface.
- A shark can see at a distance of up to 50 feet.
- Sharks have a excellent sense of smell. They are well known for their ability to detect minute quantities of substances such as blood in the water.
- Sharks can detect a concentration as low as one part per billion of some chemicals, such as certain amino acids.
- A shark's sense of smell functions up to hundreds of yards away from the source.
- Water continually flows through the nostrils, giving the shark olfactory information.
- Unlike humans, shark nostrils have nothing to do with breathing and they are not even connected to the mouth.
- Daily Activity:
- Recordings of the movements of tagged sharks suggest that most sharks have daily routines. Their greatest activity occurs during the twilight and dark hours.
- Social Behavior:
- Although sharks and batoids are basically loners, many species demonstrate various degrees of social behavior. For instance, hammerhead sharks commonly school (group together).
- Shark Attack:
- Only 32 species of sharks have been identified as attacking humans or boats. These species have 3 features in common: they prey on fish or marine mammals, grow to a large size, and frequent warmer coastal waters where swimmers are.
- In 1958, the U.S. Office of Naval Research and the American Institute of Biological Sciences set up the Shark Research Panel, a union of scientists that gathered documentation on shark attacks and compiled the information into the Shark Attack File. The Shark Research Panel documented the following...
- HUMANS BECOME PREY BY ACCIDENT. MOST SHARK ATTACKS INVOLVE PEOPLE HANDLING HOOKED OR SNARED SHARKS OR SPEARFISHERMEN HANDLING WOUNDED FISH. THROUGH SIGHT OR SOUND, A SHARK MAY CONFUSE SWIMMERS OR DIVERS FOR PREY.
- SHARKS MAY ALSO ATTACK FROM A TERRITORIAL DRIVE, WITH NO INTENTION TO FEED. A CHARACTERISTIC SWIMMING PATTERN CALLED AGONISTIC DISPLAY USUALLY PRECEDES ATTACKS OUT OF TERRITORIALITY. THE SHARK SHAKES IT'S HEAD AND SWIMS ERRATICALLY WITH A HUNCHED BACK, PECTORAL FINS POINTED DOWN, AND SNOUT POINTING UP.
- Up to 60% of shark attack injuries are caused only by the upper jaw teeth.
- Sharks may also injure victims by bumping them vigorously.
- Due to mis-information, myths, and movies, sharks have been turned into monsters that are feared, hunted, and destroyed. The TRUTH is that sharks DO NOT target man for food. Shark attacks are rare and when they do happen it is usually a case of mistaken identity with the shark mistaking a human for a prey animal. Sharks are not monsters or really man-eaters, they are simply misunderstood predators.
Tonic immobility is a behavior which occurs in sharks when a diver turns them onto their backs in the water. For some reason, turning a shark onto its back causes the shark to go into an almost trance like state. As soon as a shark is turned right-side-up again it swims away acting as if nothing had happened. Scientist have not yet discovered what causes tonic immobility in sharks, but they have theorized that being turned over some how causes an imbalance which puts the shark into this immobilized state.