Turtles are interesting animals that grow to various sizes, but all species have a body with a shell which varies in hardness accordingly. Some turtles, such as the aptly named Soft Shell variety, have shells that are more pliable and leatherier, while in others, like Snapping Turtles, the shell is much harder. Typically the shell is made of bone covered by hard plates or a leathery type of skin. Most commonly, when threatened, turtles retract their head and legs inside the shell for protection, but in some species this is not possible so they rely on their ability to deliver a very nasty bite when threatened. A snapping turtle, for instance, can certainly bite off a finger if provoked. Let’s take a further look at the behavior of these interesting animals.
There is some debate over the exact origins of the turtle shell and how and why it evolved. Some Swiss researchers postulate that the reason a shell evolved relates to prey capture, allowing the turtle to very quickly shoot the neck and head forwards in order to capture unsuspecting animals. The Swiss team studied a fossil, Platychelys oberndorferi, in which the neck bones showed that the turtle was likely able to pull its neck and head next to the side of the body. However, some other Platychelys species could pull the neck in vertically which led the researchers to theorize that the ability to retract the neck into the shell had evolved many times.
Since the turtle cannot move very fast, its best defense is obviously to hide from any possible threats. Of course, the shell is not a guarantee of absolute protection, as some predators are able to crack it open and feed on the flesh. Birds of prey often drop the turtles from a height in order to do this although only with those species that are of manageable size. While it may not be an ultimate form of safety from all threats hiding in their shell gives a sense of security to the animal in times of distress.
The evolution of a shell must be advantageous, since turtles have retained this feature through a considerable time, comprising some of the longest living creatures in existence! Likely the shell serves as an adaptation that assists the sit-and-wait type feeding where the turtle can, with head retracted, blend in quite well with the surroundings and then shoot the head out to capture prey, which do not see it. However, as discussed, not all turtles can retract their head into the shell thus it is concluded by many that it certainly could have evolved as protection against predators or from physical injury in general, whilst helping the turtle blend in with the surroundings. In many environments, both freshwater and marine, algae growing on the shell will greatly assist in this process of camouflage, enabling the continued successful survival of one of the planet’s most beautiful and bizarre creatures.