Question: When is a turtle not a turtle? Answer: When it’s a tortoise. Now that’s not strictly true because a tortoise is actually a turtle! Confused? I’m not surprised, but all will become clear.
Turtles, tortoises and terrapins all belong to the Testudinidae family of reptiles and they can, at first, all look pretty similar. The obvious differences are size and that some live in water and others on land but, once you delve a little deeper, there are many shared factors and distinct differences.
Okay, let’s compare these intriguing critters and see who comes out on top. We’ll check out the differences too.
What Is a Turtle?
Okay, let’s start with some interesting basic facts.
Did you know that the turtle dates back to the age of the dinosaurs over 200 million years ago? Bearing this in mind, it’s not surprising that they have evolved to live not only in water but also on land. In fact, the term turtle covers all reptiles who have an outer bony shell encasing their bodies. So, this includes the tortoise too.
It’s a given that what we call tortoises are exclusively land creatures and turtles tend to be aquatic and they do have lots of features in common. They also have plenty of differences making identification easier. Even taking a closer look at the shell can give us a clue to their wearer!
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It’s All About the Shell
These shells are quite amazing. There are lots of creatures who live in shells, just take a walk along a beach and check out the different shapes and sizes but, there’s nothing quite like the turtle family shell. In fact, it’s more like a piece of architecture than a shell! The turtle shell has evolved into a two piece structure: the top, called the carapace, and the bottom called the plastron. These two pieces join along each side of the animal to form a protective shell.
Unlike crustaceans, the turtle and the tortoise do not shed their entire shell as it is permanently fused to the body. Don’t worry, the shell grows with the animal and so it is impossible for the body to grow too big to fit in it and little pieces of the top layer can shed if damaged or diseased, helping to keep the animal healthy.
Dressed For Success
You wouldn’t choose to wear shorts and a tee shirt if you were going to the Arctic or your thickest, padded jacket in the Sahara- and the Testudinidae family are no exception. Although the turtle family cannot actually choose their apparel, differences in their outer shell have evolved to suit the relative habitats and protect the ‘wearer’.
For example, the high domed shell of the terrestrial tortoise may make movement slow and clumsy, a bit like going about your everyday chores wear a full suit of armor but, like the armor, it gives great protection. So, although the shape makes it difficult for the tortoise to run away from danger, it also makes it difficult for a potential predator to catch and hold the tortoise it in its mouth. Should it manage this, there’s that thick, bony casing to try and crush through and there must be an easier meal around!
In comparison, the aquatic turtle often uses speed to escape a predator and has evolved a sleek, streamlined shell ideal to enable faster speeds in the water. If speed isn’t an option, the slim shape makes it easier to slip into hidey holes between rocks and escape in that way.
So, by evolving their outer shell to suit their particular environment both aquatic and terrestrial turtles are always dressed for success.
Differences Between Turtles and Tortoises
We’ve looked at the shell, so let’s look at the bone structure now. Beginning with the back bone, both land (tortoise) and aquatic turtle have eight cervical vertebrae. However, when we get to their feet, it’s clear that the turtle has extra fingers and toes in their forefeet and hind feet. The extra span and surface area this gives helps with their swimming. The webbing is between the toes is also a bit of a give-away.
What About Their Sight?
Again, it’s all about keeping alive and avoiding injury in your particular element and eyesight is another subtle but essential difference between the aquatic turtle and the tortoise. Once more, each have adapted to suit their environment.
Looking at the aquatic turtle first, we can see here that the potential predators tend to come from two main areas: from the air where sea birds can prey on their eggs and hatchlings; and underwater, where large sharks and Killer Whales can eat the adult turtle. So the turtle eyesight has evolved to give good vision both underwater and looking upwards. Even the adjustment between aquatic and aerial vision is fast too.
Let’s compare this with the vision of the tortoise.
Predators for the tortoise, though some, such as the Raven, come from the sky, tend to be on the ground and their developed vision reflects this. Amazingly, they are thought to have some color vision, mainly in the green spectrum, but this is still being studied; however, should this prove to be true, it would be ideal when trying to identify any opportunist badger, rat or raccoon lurking in the vegetation. Incredibly, they may even see ultra violet too! This also still under research.
In a comparison between the sea and land turtle I propose this as a draw, as both animals have adapted their eyesight to suit their particular habitat.
Where Do They Live?
From tropical forests, lakes and swamps to deserts, you’ll find the turtle family resident in just about every continent with the exception of Antarctica. However, the favorite spots can be found in South-eastern North America and South Asia.
Where and How Do They Breed?
In common with other reptiles, the turtle and tortoise lay eggs. Indeed, this is the only time the sea turtles only come onto land. Again, there are subtle differences between the land and the sea animals.
The sea turtle will come onto land, lay her eggs and cover them with sand and earth. When they are ready to hatch, the little hatchlings crack their way out of the shell and proceed to dig their way to the surface and freedom. They are quite able to fend for themselves and, once out of the sand and earth, will head straight for the water. Feisty little critters!
The land tortoise will, quite naturally, lay her eggs on land. First she digs a burrow then lays her eggs and covers them over to camouflage and keep them warm. After three or four months, the hatchlings, like their aquatic relatives, dig their way up to the surface. Here’s where the sea turtle and the tortoise differ: once the hatchlings surface, they continue to be tended by their mothers for a further two months. Whereas the sea turtle gains some protection from the water, the tortoise needs the protection of a parent to survive the critical first months of life.
What’s for Lunch?
It all comes down to what’s easily available. So, the tortoise or land turtle will happily feast on beetles, invertebrates, fruit and grass but tends towards vegetarian in the main as it’s difficult to catch moving prey when you move so slowly.
The sea turtle however, having more of a speed advantage in the water, enjoys the varied diet of the omnivore and will devour anything from squid and jellyfish to a nice portion of algae!
How Long Do They Live?
The sea turtle, as with any wild creature, is difficult to track at sea and any turtles in conservatories and aquariums are usually there as a result of illness or injury so it is difficult to even hesitate a guess of their life span. It also depends on the region they inhabit and the number of natural predators there.
The oldest tortoise however, was estimated to have lived to the ripe old age of around 255 years old! This was a giant tortoise called Adwaita who lived at the Alipore Zoological Gardens in Kolkata, India until death in 2006.
As you can see, when it comes to longevity and overall lifespan, the tortoise wins this one.
Average Size: Turtle vs Tortoise
The leatherback turtle can weigh in at anywhere up to around 2,000lbs and reach a length of up to 6 feet. Meanwhile, in comparison, the giant tortoise can weigh in up to 919lbs and reach around 4 foot 3 inches in length.
How Fast Do They Move?
Sea turtles migrate thousands of miles in a year so you’d think they’d be quite nippy in the water. Surprisingly, they are slow but steady swimmers- but they can swim in bursts at speeds of up to around 35 km/hr or 22 mph, when they really need it the most.
It comes as no surprise, however, that the giant tortoise strolls along at around just 60 meters per hour! It’s a good job they’ve got that big, hard shell! The smaller, desert tortoises can scoot along at around 3-5 km/hr.
Do They Sleep?
Yes, turtles and tortoises both sleep and, in many cases in unusual places! Obviously, whether on land or in water, the place must be as safe as possible.
The tortoise will often bury itself under leaf litter to sleep or hibernate keeping the top of its shell level with the ground. A more unusual place, but just as snug, would be an old, decaying tree stump or maybe even a burrow in the winter.
The freshwater turtle, in keeping with many of the aquatic and semi-aquatic turtles, often choose to burrow into mud underwater to sleep or hibernate. As they can absorb oxygen directly from the water, the mud at the bottom of a pond can provide a comfortable environment safe from predators.
Marine turtles often wedge themselves under rocks or on coral outcroppings to provide protection whilst sleeping. Although, unlike the freshwater turtle, they need to breathe, they only need a few seconds at the surface to fill their lungs. Once this is done, they return to their sanctuary and then slow their metabolic rate down. In this way, they can remain submerged for several hours at a time.
What Do They Sound Like?
Turtles can make a wide range of weird and wonderful sounds. Some make a barking sound like a dog and some make a noise similar to a human burp! Delightful! In South America the red-footed tortoise even makes a sound like a clucking chicken!
Turtle Legend of the Native Americans
The turtle is even found in the spiritual world. In the creation myth of some Native American Tribes, the Great Spirit created their homeland by placing earth on the back of a giant turtle. Even today, North America is often know as ‘Turtle Island’.
Interesting Turtle Stuff – Useful for Quizzes!
The collective noun for a group of tortoises is called a creep. Luckily, they aren’t actually very creepy and are one of the most popular sea creatures on the planet.
The turtle family have two skeletons: an endoskeleton (internal) and an exoskeleton (external).
The scales on the carapace (shell) have growth rings on them and these can be counted, much like the rings inside a tree trunk, so that the approximate the age of wild tortoises can be estimated.
A female Galapagos tortoise called Harriet was looked after by both Charles Darwin and Steve Irwin.
Who Gets Your Vote?
So, in a nutshell, the tortoise lives the longest, the sea turtle is the fastest, and the leatherback turtle is the largest. Of course, if we’re going for sounds, I’d have to give my vote to the burping turtle! Still, however you compare them, I’m sure you’ll agree that they are all turtle-y amazing!