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| Electroreception | Feel | Hearing | Smell | Taste | Vision Electroreception Hold your hands out about three feet apart. That's about the distance at which some large sharks can sense electric fields given off by prey. Move your hands so that they are about six inches apart. Smaller sharks detect electric fields at that distance. All living things (even you) produce an electric field, given off by each heartbeat and muscle movement. A shark has special receptors located around the head that detect electric fields. These receptors can help a shark find a fish hidden under the sand by detecting its heartbeat. A shark also uses this sense to position its head and mouth when moving in for the final attack. This is the only sense a shark has that you don't share. If you wiggle your hand in a sink full of water, you can feel the water motion you create. A shark senses prey in the distance by detecting water movement made by fish or other swimming prey. Sharks have a special system, called a lateral line, that picks up the vibrations in the water. This narrow strip of sensory cells runs along the sides of the body and into the head. Sharks use the lateral line to detect the erratic motions of sick or wounded prey (easy-to-catch meals) when they are about three to 10 feet away. When prey is very close by, a shark can also detect it by bumping up against it Hearing Just because you can't see any ears on a shark doesn't mean it can't hear. In fact, a shark can hear sounds up to 0.6 miles away -- about the length of ten football fields. Sharks are particularly sensitive to the irregular, low-frequency sounds made by a sick or wounded fish, and prey in this state is an easy target. Smell Like you, a shark has nostrils. Unlike you, a shark uses its nostrils for smell only (not to smell and breathe, like you). A shark's nostrils are usually located on the underside of the snout. As it swims, water is forced through the nostrils, and particles in the water trigger signals that are sent to the brain. A shark's sense of smell is many times stronger than a human's. Sharks can detect the scent of prey that are up to several hundred yards away, depending on the speed and direction of the water current. Some sharks can smell as few as 10 drops of liquid tuna in the volume of water it takes to fill an average swimming pool! Taste While sharks probably don't count calories, many choose what they eat depending on how it tastes. A shark's mouth is lined with taste buds. Some sharks will eat anything; others will reject food because they don't like the taste (which may include the taste of humans). For a shark to use its taste sense, food needs to be close enough for it to take a bite. Vision A shark has excellent vision. In fact, its eyes are about ten times more sensitive to light than your eyes. Some experiments show that sharks can see colors, and that they may prefer bright or shiny objects. (Keep this in mind the next time you shop for a swimsuit!) Most sharks see their prey when it's about 70 to 100 feet away. To protect their eyes from a thrashing victim, some sharks (such as tiger sharks) cover their eyes with a lid, while others (such as white sharks) simply roll their eyes back into the sockets. |
| QUOTE (MAZZA_402 @ Mar 4 2006, 05:39 PM) |
| Wow. Extremely interesting. Thanks for sharing it with us, Mitternacht. |