All turtles have carapaces, also known as a shell, and for most turtles, these shells are kind of bony and hard.
A few types of turtles have shells that are more slick or leathery.
For all turtles, the shell helps to protect the sensitive body of the turtle.
Turtles are unable to live without their shells and they would be very vulnerable to damage and predators without their shells.
Some turtles and land turtles called tortoises can retract their four legs and their heads and hide inside their shells.
Different kinds of turtles do this in different ways. Some fold their necks up and to the side. Other turtles fold their neck into an S position. Some turtles cannot retract inside the shell entirely but may be able to fold their legs and heads to feel more protected.
No matter how they do it, turtles will cover themselves when a predator is nearby, when they feel threatened in general, or when they need to rest.
Some aquatic turtles cannot retract far into their shells and they are more likely to dive or swim deep underwater if they feel threatened.
Some species can retract fully or others partially but have extra-tough skin on the legs that help protect them.
Many tortoises and some turtles have thick claws that are sharp and can help them defend themselves.
Sea turtles also tend to have a flatter shell that is streamlined for swimming.
Their shells are usually not dome-shaped like a land-turtle and they cannot use their shells alone for effective protection.
They can usually move fast through the water since their legs are more like paddles and can help them get up to speed, while the streamlined shell helps them reduce friction and glide through the water.
A turtle shell also has a plastron which is the part that goes across the stomach of the turtle.
This plastron is hinged and some turtles can squeeze shut which closes the shell off to the outside.
Turtles who can retract and close their shells are quite hidden and protected.
Although turtles are fairly safe inside their shells, turtles that cannot retract fully are more vulnerable.
Even turtles that can retract and close the shell are not invulnerable.
The shell is still made of a bone-like substance and even though bones are very hard, they can be cracked, bruised or broken.
Very large birds have been known to lift a turtle high up and then drop it so that the shell breaks on rocks.
This allows the bird to turn an otherwise secure turtle into a tasty meal.
Other predators may use teeth, large claws or heavy bodies to damage the shell.
If the shell is damaged the turtle can get its skin broken leading to infection or expose too much of the body and die when damaged again.
Domestic dogs have been known to find a turtle and chew on it until the shell is fractured.
The turtle usually cannot survive and the skin of the turtle has salmonella and sometimes other toxins, so the dog usually ends up very ill as well.
Sea turtles that get trapped in fishing gear can be severely injured no matter how effective their shells might otherwise be.
Their shells can break, but most don’t even have to wait for a broken shell to be in trouble.
Just being trapped in nets or line may result in drowning.
So, the shell of a turtle is helpful, many turtles can hide in them, and they keep turtles somewhat safe!