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How Sharks Defend Themselves

Sharks are animals that we think of as predators. The lines of jagged teeth, thick skin and silent underwater speed that the species is known for are the tools of a hunter, but even the shark can become the hunted. Sharks can be threatened by sudden environmental changes or other marine wildlife and have several methods of defending themselves.

Defensive Aggression
- Human beings fear sharks largely due to media attention and popular culture. Films and stories about these animals talk about sudden attacks, wanton carnage and brazen hunters that would gravitate towards even the smallest drop of blood. The fact is that most shark attacks take place at times when the shark senses that it or its territory is being threatened. Sharks are very territorial and any encroachment in their space might be interpreted as a provocation.
The Ampullae of Lorenzini
- Small nodules called the ampullae of Lorenzini are located under the skin of every shark's nose and face. You can see them as black dots lining the nose. The ampullae detect weak magnetic fields created by other fish and even by a beating heart, which also produces a small amount of electricity. This helps locate threats that are hidden from view. Scientific research also suggests that these ampullae help the shark detect changes in water temperature, which helps it defend against natural threats, such as underwater volcanoes.
Vision and Hearing
- Sharks have very good eyesight and hearing despite the fact that their eyes seem small and beady and their ears aren't even visible. A shark has an inner ear with a range of about 800 feet. Their eyes allow them to see in murky water because of a membrane called the tapetum lucidum, which is located in the back of the eye. The membrane reflects sunlight back into the eye so that the shark can use the light more efficiently. These features are used to detect threats as much as they are for hunting.
Shark Schools
- A group of scalloped hammerhead sharks.
  
  Safety can be found in numbers and many species of sharks travel in groups called schools or shoals. Normally solitary, hammerhead sharks migrate to cooler waters in large groups during the summer. Other sharks that migrate include the spiny dogfish shark, which always travels in large schools of hundreds or even thousands of other sharks. A school of dogfish sharks is segregated according to gender and age, which also helps protect the sharks from each other.

Animals & Science