Do turtles ever leave
their shells?
February 2004
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Contrary to what you see in cartoons and storybooks,
turtles can’t actually leave their shells. Neither
can tortoises or terrapins, which begs the question:
What’s the difference between turtles, terrapins
and tortoises?
The main difference between these reptiles has more
to do with where they live than how they look. Tortoises
live their entire lives on land. Terrapins live in
brackish water (a mix of salt and freshwater).
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Loggerhead sea turtle cruises through
a shipwreck.
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Sea turtles spend their lives in the ocean, except for
a few hours each season when females come ashore to dig
nests and lay eggs. In the United States we group them all
together and call them turtles.
Turtles, tortoises and terrapins all belong to the order
testudines. They are vertebrates, which means they have
a backbone or vertebral column. In fact, their backbone
and rib cage are actually fused to their shells. So if a
turtle tried to walk off without its shell it would be leaving
its spine and ribs behind.
A turtle’s shell provides not only a home, but also
protection from predators and adverse weather. Most land
and freshwater turtles can draw their heads into their shells.
However, sea turtles are unable to do so because of the
extra muscles near their necks. These muscles help them
swim powerfully through the ocean during long migrations
or when hunting.
Turtle shells are composed of bone and consist of two main
parts. The upper part is called the carapace and the lower
part is called the plastron. The scales, or scutes, that
cover the carapace, and the arrangement of the scutes, can
help identify the species of turtle.
Each section of scutes on the carapace is actually named
to help with identification. The scutes down the middle
are called central scutes. The ones on either side are called
costal scutes, and the small ones around the edge are called
marginal scutes.
Each species of turtle has its own pattern and coloration
for shell design. Some designs are very beautiful, which
has led to serious problems for some turtles. Turtles have
long been hunted, not only for their meat but also for their
shells. This hunting has led to some species becoming endangered,
such as the hawksbill sea turtle. Its shell is highly prized
for its beauty and is used to make jewelry, bowls, glasses
frames, and many other products.
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