Zoo-Ology: Nothing but the tooth

July 31, 2011 at 2:31 a.m.

African Elephant

African Elephant

By Judie Farnsworth

Animals may have different types of teeth (like we do), only one type, or no teeth. Incisors bite and cut, canines tear and pierce and molars chew and grind. The way some teeth grow and are used is fascinating.

How can you tell an alligator from a crocodile? If you see both, in the wilds of the U.S.A., you will be in Southern Florida, the only area where they both occur.

If the jaws are closed and the fourth tooth on each side of the lower jaw sticks out, you're looking at a crocodile - hopefully at a distance.

The alligator has an empty socket in its upper jaw that hides those teeth.

Crocodiles have 64-68 teeth and alligators have between 74 and 80 teeth at a time. They are replaced as they wear down. There can be 3,000 teeth in a lifetime.

Sharks teeth are not anchored in the jaw, but grow out of its skin. They are in several rows and replaced throughout the shark's life. As the front teeth wear away or fall out, the teeth in the second row move forward. A tiger shark may shed more than 2,000 teeth in a year. No need to floss here.

Some animals, like beavers, also use their teeth for building. Their sharp incisors cut through tree trunks used for building dams. Their teeth grow continuously and are always sharp.

Elephants' tusks are actually elongated incisors (their only ones) and are used in various ways: digging, lifting, stripping bark. They're set deeply in the skull with only two-thirds showing. Male's tusks usually grow continually, often weighing more than 100 pounds and measuring more than 10 feet long. Female's tusks may stop growing at adulthood.

Note, not all elephants have tusks.

Elephant teeth are unique.

They have six sets of molars in a lifetime and a distinctive cycle of tooth rotation. At certain ages, an elephant's molars (developed at the back of the jaw) move forward to replace molars that have worn down to a kind of shelf. The roots are absorbed and they eventually break up and are pushed out.

Only two molars are in wear at the same time and have a ridged surface. The molar of a bull African elephant can weigh 10 pounds. An elephant that outlives his sixth molars can starve with no means to grind food. The sixth molars appear at about 30 years and last about another 30 years. A forward-backward chewing movement grinds food.

Why is that cow chewing in circles? It's actually a side to side movement. A closer look will show eight incisors in the bottom jaw, but no teeth on the top front. Instead, there's a horny dental pad. There are molars farther back on the top and bottom for a total of 32 teeth. The cow tears grass and grinds it between the two parts.

The giant anteater and some whales, like the baleen whale, have no teeth. Just like a bird's bill can suggest what it might eat, so can an animal's teeth.

Who has the most teeth? In the ocean, the long-snouted spinner dolphin wins with as many as 252 teeth. On land, the giant armadillo wins with as many as 100 pearly whites.

The heaviest pair of teeth from a species still in existence belonged to an African elephant. Together they or tusks weighed 465 pounds.

Come see some of the teeth at The Texas Zoo. The daily reptile show at 11 a.m. has some great ones.

Judie Farnsworth is a long time volunteer at the Texas Zoo specializing in educational programs.



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