The Teenage Mutant Ninja Turtles, famous comic heroes from the 80s are living in the sewerage system of New York. But are they really turtles? Or maybe tortoises? What is the difference between both? Yes, there is one.
Let's start with what they have in common. Yes, turtles and tortoises are reptiles. They are referred to as Chelonias, a term originating from the Greek word for tortoise. Both have scales and carry a shell for protection from their predators. They lay eggs, and they are ectothermic, which means they need an external heating system - like the sun. Chelonians can be found everywhere, from deserts to oceans.
And that is basically where the main difference lies. The term turtle or tortoise relates to where the species lives and how it uses its habitat.
Turtles spend most of their lives in the water, and commonly have webbed feet for swimming. Sea turtles rarely leave the ocean, except to lay their eggs on the beach, but other specie that live in freshwater ponds or lakes are more likely to go ashore. They might climb onto rocks to get some sun, or dig into mud if the weather is too cold.
A tortoise on the other hand is a land-dweller. It feeds on shrubs and grasses and has no webbed feet, but round and stumpy ones for walking on land. Tortoises tend to burrow into the ground when it gets too hot outside.
On that basis, and taking into account that New York's drainage system is neither particularly dry nor hot, the question mark remains hanging over the Teenage Mutant Ninja guys. Then again, they are definitely not always under water. So wouldn't that make them land lubbers?
We'll leave it to you to decide.