Oregon Zoos, Aquariums and Wildlife

Sharks have been around since the Cretaceous Period, about 64 million years ago when dinosaurs ruled the earth.

Sharks swim in every ocean of the world, from warm tropic waters to icy polar seas.

Sharks are fish. Some sharks lay eggs, but most sharks give birth to live young. Shark babies, called pups, are on their own from the moment they are born. At birth, newborn pups are excellent swimmers and are able to find food and fend for themselves.

A shark doesn't't have a bone in its body. Its skull, spinal column and fins are made of cartilage, a tough but light and flexible elastic material that is also found in Print nose and ears.

A shark has a very good sense of smell.

Most sharks have very good eyesight, particularly sharks that feed near the surface of the sea during the daytime. Sharks that live in the dark depths of the ocean may also have much larger eyes than those that live near the surface. Sharks that spend most of the day resting on the bottom of the sea or live in murky water probably don't rely on sight as much as their other senses.

Most sharks do not blink. The upper and lower eyelids of most shark cannot move at all, but their eyes can be rotated for protection when feeding. Some kinds of sharks have a third eyelid, called a nictitating membrane which is a moveable shield that completely covers the eye as the shark feeds.

A shark is always teething; it may lose between 12,000 and 30,000 teeth during its lifetime. Its teeth aren't attached to its jaws and are continually being replaced. It is like having a conveyor belt of teeth.

Not all sharks have sharp teeth. Each kind of shark has teeth suited to its life style. Teeth may be knifelike or fork-like, sharp or blunt or rounded, large or small and the teeth of some young sharks may differ from the adults. Because the number and shape of the teeth differ in each kind of shark, scientists can use teeth to identify a shark.

Sharks eat only between 2.7% and 5% of their body weight every 40 to 80 hours. If you ate like a shark you would only have a hamburger and fries every two to three days.

Sharks have relatively large, complex brains. They learn by investigating their surroundings; like you, sharks learn through experience. The ability to learn makes it possible for sharks to tackle situations that cannot be dealt with by instinct alone.

Sharks don't have voices but they communicate with each other through body language. When a shark lowers its pectoral fins, hunches its back and swims with exaggerated movements, it is delivering a warning. Sharks may make similar displays or slap the water with their tails when faced by another shark or large unfamiliar object.

Mako sharks are the fastest sharks. They are also able to leap 20 feet above the surface of the water and to do that they have to reach a speed of 20 miles per hour or even faster! Sharks have cruising speeds, but when chasing fish or fleeing from an enemy they can swim much faster. But sharks can't stop quickly, and they cannot swim backwards.

Hammerhead sharks are the weirdest-looking sharks. The flattened head of hammerhead sharks may have evolved to give it lift when swimming forward and its head holds more electrosensory organs – which the shark needs to navigate long distances in the open sea and to find food that is well-camouflaged or hidden beneath the sand. The hammerhead shark's favorite food is squid and having widely-separated eyes may be a very good design when Print favorite food has tentacles. Another strange shark is the goblin shark which is pink with blue fins and has a long blade-like nose.

Not all sharks are dangerous. Only 3 of the 370 different kinds of sharks found in the oceans have been involved in attacks on humans—the great white shark, the tiger shark and the bull shark.

Humans are far more dangerous to sharks than sharks are to humans. 58 people were attacked by sharks in 2006—Four people were killed by sharks. However, people kill more than 100 million sharks each year. The senseless slaughter continues because most people don't realize how important sharks are to the health of our oceans – and to our planet!