Truths about Sharks

TRUE OR FALSE

1.Sharks eat a lot.
2. Sharks have good eyesight and can see in the dark.
3. Sharks have a poor sense of smell.
4. A shark grows thousands of teeth in its lifetime.
5. Sharks often attack humans.






1. False: Sharks eat about 2% of their body weight each day, a little less than a human eats.
2. True: Sharks see quite well and see better in the dark than people do.
3. False: Sharks have an excellent sense of smell. They can smell one drop of blood in 100 liters of seawater.

4. True: A shark may lose thousands of teeth in its lifetime. Sharks have several rows of    teeth  constantly growing and replacing the ones they lose. When a tooth is lost, the tooth behind it moves forward as though on a conveyor belt.
5. False: Attacks on people are very rare. You have a better chance of being struck by lightning, killed by honeybees or choking to death on your dinner than being attacked by a shark. Relax and enjoy the water.

Shark Teeth Facts

 

 What's so special about a shark's tooth?

If you don't know much about shark-tooth collecting, then you may not know that these relics are more than just teeth -- they're fossils. Sharks have been living on Earth for about 400 million years. When a shark dies and its cartilage dissolves, the teeth fall to the bottom of the ocean and get covered with sandy sediment. This sediment prevents oxygen and destructive bacteria from reaching the tooth, and it fossilizes over the course of about 10,000 years. That's why most of the teeth that are found and collected aren't white, but gray, black or brown -- the color of the sediment. The tooth absorbs the minerals in the sediment and these minerals eventually replace the dentine and enamel that makes up the tooth. Voila, you have a fossil on your hands.

Like all other fossils, shark's teeth can be valuable, so they're readily bought, sold and traded by enthusiasts and collectors. The most valuable of all is the tooth of the giant megalodon shark. This bad boy was a prehistoric beast that makes the modern great white look like your average goldfish. Great whites these days vary in size from 7 to 20 feet (2 to 6 meters). The prehistoric megalodon may have grown to a whopping 60 feet

The tooth of the megalodon ranges in size from 3.5 to 7 inches (89 to 177 mm) in length and can weigh more than a pound (.4 kg). Locating any megalodon tooth is a great find, and anything over 4 inches is rare and valuable. These teeth can go for as much as several thousand dollars each on the auction Web site eBay, depending on the size and the location where it was unearthed. The other factor that determines the value of the tooth is the shape that it's in. Even though teeth are fairly well ­preserved as fossils, they can be slightly eroded and contain chips and cracks from undersea rocks and coral.

So one reason people collect shark teeth is the shear monetary value. There are dozens of Internet sites devoted to the sale of these collectibles. Another reason is that on any given hunt, you may find a tooth from a giant, prehistoric predator that's 10 to 50 million years old. Most people would agree that digging up a 1-pound fossilized shark tooth as big as your hand is pretty cool.

What do sharks teeth look like?  I have never seen an actual fresh white shark tooth on the beach, but have found many fossilized sharks teeth. 
Color – for fossilized shark teeth, the color of the teeth will depend upon the materials in which the original teeth were buried.  I have found many of these fossils ranging in color from that of very light sand, to brown or gray, to pitch black.  In Onslow Beach, the teeth that turn up are largely pitch black.  In fact, when wet, they generally have a shine to them, almost like wet black spray paint.  For the Onslow Beach area, color may be the most important factor to target.   

Shape – Based on the movie Jaws, the cartoon character Mister Jaw, and what I learned from billboards, I began searching for triangle shaped objects.  It turns out that not all teeth are shaped like triangles.  In fact, most teeth I have found are not neatly triangular in profile.  Some internet research quickly revealed that the different shapes of teeth reflect different species of shark.  Perhaps more importantly, it is common for a portion of the gum to be attached to the teeth, which, depending on how much gum is there, can give the tooth a very odd and non-triangular outline.

Shark Tooth Hunting

The teeth of sharks are not attached to the jaw, but embedded
in the flesh, and in many species are constantly replaced
throughout the shark's life. When they lose a working tooth it
will be replaced by the next tooth behind it. All sharks have
multiple rows of teeth along the edges of their upper and lower
jaws. New teeth grow continuously in a groove just inside the
mouth and move forward from inside the mouth on a "conveyor
belt" formed by the skin in which they are anchored. Typically
a shark has two to three working rows of teeth with 20 to 30
teeth in each row, although a whale shark has about 300 teeth
in each row. The replacement rate has not been measured in
most sharks but normally the teeth seem to be replaced every
two weeks. The lemon shark replaces its teeth every 8–10
days, and the great white shark replaces its teeth about every
100 days for young sharks and about every 230 days for old
sharks. Most sharks shed individual teeth, but the cookie-cutter
shark sheds the whole lower jaw at once. The shape of a shark's
tooth depends on its diet; those that feed on mollusks and
crustaceans have dense flattened teeth for crushing, those that
feed on fish have needle-like teeth for gripping, and those that
feed on larger prey such as mammals have pointed lower teeth
for gripping and triangular upper teeth with serrated edges for
cutting. The teeth of plankton-feeders such as the basking shark
are greatly reduced and non-functional