Sharks have powerful senses that make them such successful predators. Besides the standard senses, they have also developed a remarkable ability to pick up the electrical signals that are produced by all living things. This process is called electroreception.
Electrical receptors are located on a shark’s snout and lower jaw, where tiny pores filled with a jelly-like substance, called the ampullae of Lorenzini, pick up even the weakest electrical fields. Living things emit electrical fields whenever they contract their muscles. This 6th sense is so acute sharks can detect and find fish which are buried in mud on the ocean floor.
Sharks perceive weak changes in electrical currents that wounded or struggling creatures produce. Researchers think this is why sharks can be attracted to humans playing in the water. Their movements produce similar electrical messages as those given by wounded creatures.
Researchers also believe this sixth sense helps sharks navigate the ocean, sensing the electrical field produced by ocean currents , reading them like a map. This ability has intrigued the military, and they are would like to develop a similar technology, which would be more effective than sonar.
Sharks can “hear” all over their bodies. From their heads to their tails they have special organs just beneath the skin which contain sensitive hair cells. These cells are triggered by the tiniest change in water pressure caused by anything in the ocean, from other fish to humans.
It also allows them to detect sound from up to several miles away, especially the sound of struggling fish, which gives off a low frequency. This frequency is the same one that humans playing in the water create. This sound can attract sharks from far away in a matter of minutes.
Sharks are curious creatures, and they will travel several miles to investigate potential prey. It is typical for a shark to bump things with its snout when it’s trying to determine if it’s edible. It will even take a taste bite to see.
In attack mode, a shark’s eyes roll back inside their sockets or they’re covered by a protective membrane. Now blind, a shark relies on its extra sensory ability to pick up electrical signals produced by its prey. These signals guide the shark’s jaws in the right direction.
Sharks have a sense of smell that is so powerful it is estimated they can smell one drop of blood in a million drops of water, from nearly half a mile away. It is even believed that some sharks come up to the surface of the ocean in order to smell the air.
Sharks can see in nearly every direction because their eyes are wide apart and they constantly move their head back and forth in a zig zag motion as they swim. Like humans, they have binocular vision, which means they have depth perception and can accurately judge distance. Many species have color vision, including the Great White. Shark eyes are designed to see in very little light and are 10 times more sensitive to light than humans.
Carwardine, Mark. The Shark Watcher’s Handbook. Princeton, New Jersey: Princeton University Press. 2002.
http://www.enchantedlearning.com/subjects/sharks/anatomy/Senses.shtml Enchanted Learning.
Fox, Andrew. http://www.diveplanet.co.nz/greatwhitesharksensors%2Fgwssm.asp Dive Planet NZ.
Lowe, Christian. http://www.defensetech.org/archives/001256.html Defense Tech.
