How Can You Tell a Terrapin from a Tortoise?
All turtles, tortoises, and terrapins are reptiles. They all have scales, lay eggs, and are ectothermic; they vary in size from fitting in your hand to about 1,800 pounds (817 kilograms). So why are there different names? Those common names usually refer to differences in where the species live and how they use their habitat.
For most Americans, the term ‘turtle’ describes the Chelonians that are aquatic or semi-aquatic. The term ‘tortoise’ describes a Chelonian that lives primarily on land. ‘Terrapin’ can describe some freshwater or saltwater turtles, but is not often used.
If you were in Australia, you might call all of the turtles ‘tortoises,’ and in Britain, a ‘turtle’ would mean a saltwater species and a ‘terrapin’ would be a freshwater species. The species living on land are called tortoises and the species that are aquatic or partially aquatic, turtles.
You can tell a terrapin from a tortoise by its much more streamlined shape, and because, unlike the tortoise, it lives in fresh water as well as on land. Both tortoises and terrapins belong to an ancient order of reptiles called Chelonia, which includes 244 different species.
Their shells are in two sections, the upper domed portion or carapace being made up of a series of horny shields that form a regular pattern. The tortoise’s shell normally has a high round dome, while that of a terrapin is flattened and streamlined. Some terrapins have slightly webbed feet. They are also faster on land than tortoises.
In both reptiles the head is covered with scaly skin, and the eyes are exceptionally dark and can be closed behind two eyelids. They also possess a third, almost transparent, skin that can be moved across the eye for protection. They have no teeth but their jaws are sharp, and they have a good sense of smell. They are quite intelligent, learn to recognize their owners, become fairly friendly, and are often kept as pets.