Why (And How) Tortoises Live So Long?

Tortoises are known for their longevity, with some species living for more than 100 years. This has long been a source of fascination for scientists and animal enthusiasts alike, leading to the question: why do tortoises live so long?

The main reason why tortoises live so long is that they have a very low metabolic rate, meaning that they don’t need to consume as much food or oxygen to survive. The slow metabolism also helps to reduce the amount of cellular damage that occurs over time, which can lead to aging and disease.

There are other important factors that allow tortoises to live so long, like their ability to store large amounts of nutrients and energy, the ability to hibernate, the inability to produce body heat, their thought protective shell, and their ability to adapt to a wide range of environments.

How Tortoises Live So Long

Jonathan, the 190-year-old Seychelles tortoise in his youth (left), and today (right). Photo: Guinness World Records

Now, let’s take a closer look at each thing that allows tortoises to live so long. Starting with the most important one, their slow metabolic rate.

Metabolic Rate

A simple way to describe the metabolic rate is the rate at which the whole internal body moves. The faster the metabolic rate is, the more energy it will need to function properly, so the more food you will need to eat. And the same goes for oxygen.

The main reasons why tortoises have a lower metabolic rate are the fact that they are cold-blooded, which means that they can’t generate their own body heat, and that they move very slow.

Most animals use a lot of energy to keep their bodies at the optimal temperature, but tortoises, like all reptiles, don’t do that. What they do instead is they spend a few hours every day basking in the sun, or in the case of pets in the basking area where the sun is replaced by a heat bulb and a UVB bulb.

Overall, for tortoises, this tradeoff seems to be going well. As there are usually a lot of good places for them to bask, and in the winter they will hibernate And as a result they get to live a longer life.

One of the biggest advantages of a slower metabolic rate is that there will be less cellular damage, which in most cases translates to aging. Basically, the slower their body moves, the smaller the chances that cells will get damaged, which means that they will be able to live for longer.

Storing Energy

One of the main advantages of a low metabolic rate is that it uses less energy. Needing less energy, means that you need less food. But tortoises don’t wait until they get hungry to start looking for food, they do that constantly.

Tortoises are opportunistic feeders, this means that they will eat on every opportunity that they get. But they don’t do this due to hunger or gluttony, no, they do it because they are very bad at hunting. And there is no way to know when the next chance might appear.

Tortoises are excellent at defending themselves, but when it comes to catching food, they are not that great at it. So if a tortoise can eat two or three full meals in a row, it will do it since, there is a real chance that it will have to wait months until it gets the chance to eat again.

Most tortoises are omnivores, so they will eat fruits, vegetables, plants, as well as fish and insects. But in most cases fish and insects are preferred over fruits, vegetables and plants. This is especially true for younger tortoises who might not eat them at all, since they need a lot of protein in order to grow, and plants have little to no protein.

Hibernation

One key ability that allows tortoises to live so long is that of hibernation. And tortoises do this because their inability to produce body heat, and the lack of food during the winter season.

When the weather starts to get cold, the metabolism of a tortoise will automatically start to slow down even more. So they will need even less oxygen and food in order to survive.

Most tortoises will hibernate anywhere from 3 to 5 months. And during this time they will basically enter a very profound sleep, during which their heart beats extremely slow, their lungs inhale and exhale less air, and their body uses little to no energy, just to keep the tortoise alive for the next months.

Tortoises are able to this because they reduce their metabolic rate. But reducing the metabolic rate can also have some unpleasant side effects. One of the bad things that happen is that they have a hard time getting rid of the lactic acid that accumulates. Lactic acid is the same thing that gives us muscle soreness, so you can imagine how unpleasant it can be for the tortoise to wake up after a long sleep with muscle cramps all over the body.

To neutralize the lactic acid, tortoises use magnesium and calcium that they’ve stored in their shells. If they didn’t do that, the lactic acid builds up would be too big, and they wouldn’t be able to wake up from hibernation at all.

The calcium and magnesium that they used would have helped them grow, but because getting rid of the lactic acid was more important, they had to use it for that. This is another bad side effect, tortoises won’t be able to grow when they hibernate. And growing isn’t something superficial for tortoises, it’s something that can save their lives. The bigger they get, the fewer predators will come after them.

Adaptability

Tortoises are one of the most, if not the most adaptable in the world. At the moment there are 49 different tortoise species, which can be found anywhere, ranging from arid deserts, to the cold tundras, to isolated islands in the middle of the ocean. The only palace in the world where you won’t find a tortoise is the Arctic.

Tortoises are able to adapt very easily to a new environment, and this allows them to live long and prosperous lives anywhere in the world.

How to Tell the Age of a Tortoise

So, now that we covered why tortoises are able to live so long, let me share with you a few tricks that can help you figure out how old a tortoise is.

Counting the Rings Method

This is a very simple and quite accurate method that can be used by anybody to guess the age of their tortoise.

The rings that you can count are present on the shell of most tortoises. Here are a few pictures.

After you are done counting the rings, just divide that number by 2 and you’ve got the age of your tortoise. It’s that simple.

But as you can imagine this method is not 100% perfect, and the reason for this is that at one point the tortoise will stop growing and the new rings will be harder to spot.

The rings are formed as the tortoise grows. And since tortoises don’t grow at the same rate all year round, this will create some visual signs, in this case, the rings.

After a certain age tortoises will slow down their growth considerably, and at this point the new rings will be harder to spot, so it will be easier to make errors when counting them.

But telling the exact age of a tortoise is extremely hard, and this method does a pretty good job. Even if it doesn’t work too well on old tortoises, you should still get a pretty good estimate, and in the case of younger tortoises, you should be able to get an exact age.

But as good as this method is, there are other methods that can be just as good if not even better, so let’s take a look at them as well.

The Size Method

This is another very simple yet effective method, but unlike the previous method, it requires some knowledge about the species of the tortoise, which I will provide.

So to put this method into practice, you simply have to measure the shell of your tortoise and compare it to a table.

Here are 3 tables, one for Red-Eared Sliders, one for Painted Turtles, and one for Box Turtles (which despite their name are actually tortoises).

Red-Eared Sliders

Red-eared sliders are definitely the most popular pet turtles, and one of the reasons for this is that people get them when they are still babies, and most of them are no bigger than 1 inch (2.5 cm). But most people will find out soon enough that they won’t stay that small for long.

During their first year, red-eared sliders tend to double or triple in size, reaching a size between 2 and inches (5 and 7.5 cm).

After that, the growth continues at an accelerated rate, for the next two years, as most red-eared sliders continue to grow as much as 2 inches per year. By the age of 3, most red-eared sliders have a size of 7 inches. At this point, the growth slows down to about 1 inch per year, and it continues that way until the turtle reaches the age of 5.

After the age of 5, the growth slows down, as most turtles grow less than half an inch per year. And they will continue to grow at this rate up until they reach the size between 8 and 12 inches, which is their maximum size.

After this point, very few red-eared sliders continue to grow any further, and if they do, they do it at a very slow pace, which is bearly noticeable.

Painted Turtles

Compared to red-eared sliders, painted turtles are much smaller, only reaching sizes of around 6 inches (15 cm). And as a result, their growth rate is also slower. But unlike red-eared sliders who reach their maximum size around the age of 8, painted turtles continue to grow, until they reach the age of 20.

Like most turtles, painted turtles start life with a size of about 1 inch (2.5 cm). And during their first tear, they will reach a size of about 2 inches (5 cm).

For the next two years, up until the age of 3, they will grow at a rate of 1 inch (2.5 cm), per year. After that, the growth rate will go down a lot.

Most painted turtles reach a size of 4 inches (9 cm) at the age of 3. But during the next 7 years, most of them will only grow one more inch, reaching the size of 5 inches.

Most painted turtles reach their maximum size, of 6 inches (15 cm) when they are 20 years old.

Box Turtles

Box turtles are also a smaller species, reaching a maximum size of 6 inches (15 cm). But compared to painted turtles, they reach their maximum size much faster.

During their first year, most box turtles will reach an average size of 2 inches, after which they will grow about 1 inch per year, up until they reach the size of 4 inches (9 cm). And this is the point when the growth slows down.

After the age of 3 years, the growth will slow down to about 0.4 inches per year (1 cm), up until they reach a size of about 6 inches (15 cm), at which point the growth stops.

But as you can see, this method has its limitations. The first one is that once the tortoise reaches its maximum size, you can’t really use this method anymore.

The second one is that tortoises can have their growth stopped by external factors like lack of food, long winters, etc.

So, while this method is great if you want to find out the age of a young tortoise, it’s not so useful when it comes to older tortoises. But it can at least give you an idea of the minimum age.

One more problem with this method is that depending on the species of the tortoise, sometimes females can be significantly larger than males, but in order to find out if a tortoise is male or female you will have to wait for them to reach maturity, since that is when the visual signs appear, but by that point, the tortoise has almost reached its maximum size.

If you want to know how to find out if your tortoise is male or female, you should check out this article: How to Tell If Your Tortoise Is Male or Female (with pictures).

Dietary Preferences

Most tortoises are omnivorous, meaning that they can eat both plant matter (fruits, vegetables, etc) and meat. But as their age changes, so do their dietary preferences.

Younger tortoises that are still growing will always prefer meat to anything else. This is because meat contains a lot of protein, which is what tortoises need in order to grow.

On the other hand, older tortoises, who stopped growing, are not as thrilled about meat anymore. They will still eat it if you put it in front of them, but if they have to choose between chasing a fish or eating a plant that is in front of them, they will go for the plant.

Visual Cues

Visual cues can tell you a lot about the tortoise’s age.

One of the first differences that you will notice between a younger and an older tortoise is their speed. Older tortoises tend to move significantly slower than a younger tortoise.

Another difference is in the shell, the older a tortoise is, the more worn out the shell will look, due to scratches and daily wear and tear.

Left side young Red-Eared Slider, Right side old Red-Eared Slider

Another visual difference comes from the colors of the shell. Most tortoises start their life with very bright and intense colors, and as they age those colors will continue to fade. Even after the tortoise has reached its maximum size, the colors will continue to fade out.

Other Methods

By looking at those 4 things, you should be able to have a pretty good guess of how old a tortoise is just by simply looking at it for a few seconds.

But f you want to be even more exact you can check out this article in which I cover even more methods: How to Tell the Age of a Tortoise (Beginners Guide + Pictures).

What Can Decrease a Tortoises’ Lifespan?

A tortoise’s lifespan can be shortened by a lot of things, the most significant of which being wounds. A tortoise’s shell, has the ability to heal itself, but that ability is limited. If we are talking about a small scratch, in a year or two you wouldn’t even be able to tell that it was there, but a very large crack won’t ever heal completely, and this will make the tortoise vulnerable.

Another big problem that can affect a tortoise is a disease or an infection. When a tortoise catches a severe disease, there is a good chance that it will never recover from it. And if it does, its internal organs will be affected and weakened, making it less likely for the tortoise to survive the next.

Another serious problem that tortoises face is starvation and malnutrition. While tortoises don’t eat that much, and in general they overeat just to make sure that they won’t starve, there is still a good chance that it will happen. Most tortoises live in areas that in one way or another end up being affected by human activity, and the result is usually that there is less food for them. And even if they still find something to eat, it might not have all the nutrients that they need, and this will lead to malnourishment.

And the biggest thing that reduces a tortoise’s lifespan, at least in the wild, are predators. Tortoises, like most animals, are hunted and eaten by other animals. Lucky for them, they are very good at defending themselves, but from time to time their defenders will fail. But that’s just the circle of life.

Final Thoughts

The main reason why tortoises live so long is their slow metabolic rate.  While there are other important factors like their ability to store large amounts of nutrients and energy, the ability to hibernate, the inability to produce body heat, their thought protective shell, and their ability to adapt to a wide range of environments. The main reason is the slow metabolic rate, which make tortoises age at a lower rate.

I hope this article answered your questions regarding how and why tortoises live so long. But in case you still have questions, or you would like some help, don’t hesitate to ask in the comment section below, I regularly check the comment sections and answer all questions.

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