Sloth Versus Giant Tortoise

Sloth Versus Giant Tortoise

Wait — we’re comparing a sloth with a reptile? It’s never been done before! What could a sloth possibly have in common with a reptile? On the face of it, there’s not much that a warm-blooded sloth could share with a cold-blooded reptile. But these slow and charismatic creatures might be more similar than you’d think.

There are just two surviving species of giant tortoise: the Galápagos giant tortoise and the Aldabra giant tortoise.

The Aldabra giant tortoise is now found in the wild only in the Seychelles, although they used to be found on many islands in the western Indian Ocean.

In the Galápagos Islands in the Pacific Ocean, there are two distinct types of Galápagos giant tortoises: domed tortoises and saddlebacks.

Are sloths and giant tortoises related?

No! Giant tortoises are reptiles in the order Testudines, whereas sloths are mammals in the order Pilosa. Reptiles and mammals diverged from one another around 325 million years ago, during the time the supercontinent Pangaea existed.


Galapagos Giant Tortoise Chelonoidis nigra. Santa Cruz Island, Galapagos Islands, Ecuador

Where do they live?

Giant tortoises used to inhabit every continent apart from Antarctica, but today they’re found only in the Galápagos Islands of Ecuador, and the Aldabra Atoll islands in the Seychelles.

Sloths and Galápagos giant tortoises both once shared the same landmass. Scientists believe that Galápagos tortoises most likely migrated from South America to the Galápagos 2 to 3 million years ago. But that’s where the similarities end when it comes to the habitats of sloths and giant tortoises.

Tree-dwelling sloths need a warm and humid habitat, whereas Galápagos giant tortoises live generally in dry and arid climates. Aldabra giant tortoises live in scrubland, mangrove swamps, and open grassy areas.


Three-fingered sloth in the canopy. Suzi Eszterhas.

How heavy are they?

A giant tortoise has yet to be seen climbing a tree! They prefer to stay firmly on the ground. In fact, they have little choice. These stocky tortoises really are giants, weighing up to around 700 pounds. But that’s still nothing compared to the prehistoric ground sloth Megatherium, which weighed up to 4 tonnes!



Their thick, sturdy legs help them to carry around this weight, and as their shells are made up of honeycomb structures that enclose small air chambers, the shell itself doesn’t present the tortoises with too much of a problem when it comes to carrying it around.


giant tortoise
Aldabra Giant Tortoise Geochelone gigantea

How long do they spend resting?

As giant tortoises are cold-blooded, they like to spend a good amount of time basking in the sun. They sunbathe for 1—2 hours after dawn to absorb the sun’s heat through their shells before foraging 8-9 hours a day. In total, they rest or sleep for nearly 16 hours per day.

Sloths by comparison sleep for just 8—10 hours a day.



Sun seekers

Like tortoises, sloths are poikilotherms — animals that are unable to regulate their body temperature.

Although sloths live in warm, tropical environments and have thick coats to help them thermoregulate, they’re unable to shiver when cold, so need to bask in the sun to warm up — much in the same way that giant tortoises do.

If sloths become too cold, they will stop being able to digest food and can starve to death, even on a full stomach!


sloth basking
Sloths also bask under the sun / Photo by Cristhian Chentiko


Like sloths, giant tortoises will seek shade to help them to cool down, but even better is a muddy puddle to wallow in — perfect to escape the midday heat.


Sloths and tortoises, who is the slowest?

It’s a close call. The sloth boasts the title of the world’s slowest mammal moving at a mere 0.27 km per hour, while the giant tortoise races ahead at a heady 0.3 km per hour.

Like the sloth, giant tortoises have a very slow metabolism. It takes them up to 21 days to digest food, while the sloth, which boasts the lowest metabolic rate of any mammal, takes 30 days to digest just one leaf!


What do they eat?

Giant tortoises are predominantly herbivores. Aldabra giant tortoises eat grasses, leaves, woody plant stems, and fruit, but they’ve occasionally been observed eating small invertebrates and carrion, including the bodies of other dead tortoises! You wouldn’t catch a sloth doing that.

The diet of a Galápagos tortoise consists of cacti, grasses, leaves, lichens, milkweed, fruit, and prickly pear cactus. They’ve been found to play a key part in shaping their ecosystem by dispersing plant seeds in their dung.


Galapagos Giant Tortoise Chelonoidis nigra. Santa Cruz Island, Galapagos Islands, Ecuador. Suzi Eszterhas.

Little water is available in the giant tortoise’s natural habitat, so they get most of their moisture from their food. This is similar to sloths, obtaining most of the water they need from the foliage they eat.

Amazingly, the slow metabolism of the giant tortoise and their ability to store large amounts of water means that they can survive up to a year without eating or drinking!


How long do sloths and giant tortoises live?

Although no one knows how long sloths actually live for, it’s suspected that they might live to well over 50 years old in the wild — an impressive age. But that’s nothing compared to giant tortoises.


sloth fest sloth selina


They are among the world’s longest-living animals, with an average lifespan of 100 years or more. Lonesome George, a Galápagos giant tortoise, died at 152. A spring chicken compared to Jonathan the Aldabra giant tortoise, who recently celebrated his 190th birthday.


Are they social?

Like sloths, giant tortoises like to lead peaceful and quiet lives. Their lives revolve around eating, relaxing in the sun, or wallowing in puddles. Aldabra giant tortoises and domed tortoises in the Galápagos are more social and often found in herds, in contrast to more solitary and territorial saddleback tortoises.


giant tortoises
Galapagos Giant Tortoise Chelonoidis nigra. Santa Cruz Island, Galapagos Islands, Ecuador

What problems do sloths and giant tortoises have in common?

Sloths and giant tortoises both face threats from habitat loss due to human development.

Galápagos giant tortoises have historically suffered huge declines due to exploitation by whalers, pirates, traders, and fur sealers. They were a source of fresh meat that could be kept alive for months on end without any food or water — ideal for long days out at sea. They were also killed for their oil, which could be used for burning lamps.


giant tortoise
Galapagos Giant Tortoise Chelonoidis nigra. Santa Cruz Island, Galapagos Islands, Ecuador.


The introduction of different species have also had a terrible impact on giant tortoise populations. Feral dogs can attack tortoises, rats predate tortoise eggs while livestock such as cattle and horses trample their nests. Goats compete with the tortoises for food, and fencing and roads affect migration their migration routes.

Two species of giant tortoise are sadly thought to have gone extinct: the Floreana giant tortoise and the Pinta tortoise. The last known Pinta tortoise was Lonesome George, who died in June 2012.


What can be done to protect them?

In Ecuador, the Galápagos National Park was established in 1959 in an effort to protect its unique flora and fauna. Scientists have collected eggs from the wild in the park and incubated them at the Charles Darwin Research Station. Bringing the eggs into captivity ensures that the newly hatched tortoises can grow big enough to escape attacks from rats and dogs when they’re released into the wild. Eradication campaigns are also being undertaken to remove introduced species such as rats.

Scientists are also working to better understand the tortoise’s migration routes, in an effort to protect more of their habitat. As with sloths and any other animal, the better we understand them and their needs, the better we are able to help them and ensure their survival.


-Samantha Stocks

SloCo Collaborator