If you found an empty turtle shell, experts say the exact strength of a shell depends on the size of the animal. A box turtle can support up to 200 times its weight and it will take thousands of pounds worth of pressure in order to crush it. Though sea turtle's shell is softer than the land turtle's, this enables whales and sharks to easily break it during an attack.
Of all the animals with backbones, turtles are the only ones that have a shell, made up of 59-61 bones covered by plates called scutes, which are made of keratin like our fingernails. The turtle cannot crawl out of it since the shell is permanently attached to the spine and the rib cage.
The shell’s bottom is called the plastron, and the top is the carapace. Turtles can feel pain and pressure through their shells, just as you can feel pressure through your fingernails.
Some turtles can pull their heads, feet, and legs inside their shells, they are known as "hidden-necked turtles.” In order to make room inside the shell, they occasionally have to exhale air out of their lungs, which makes a hissing sound.
Other turtles cannot pull their legs or heads into their shells. Some of these have long necks and safeguard their heads by tucking them sideways into the shell, they are known as "side-necked turtles.” Tortoise shells are not as heavy as you may think. The shell contains numerous tiny air chambers, which makes it a little lighter.
If you're considering adding a turtle or tortoise to your family or are just bringing one home for the first time, the PetSmart turtle and tortoise guide has the information you need to help you and your pet start off on the right foot with tips on how to house, care and feed your new friend.