Galapagos Tortoise – The Story Behind These Gentle Giants
The Galapagos Tortoise
No Galapagos creature captures the imagination quite like the giant Galapagos Tortoise. These gentle giants are true icons of the Galapagos islands, and a great example of species evolution. Of course the most striking feature is their impressive size, but that alone does them an injustice. The Galapagos Tortoise also has plenty of charisma and character. They can be surprisingly bold and inquisitive fellas, and boast universal appeal that makes giant Galapagos tortoises so popular with visitors.
There are 15 different Galapagos tortoise species, all endemic to the Galapagos Islands meaning you can only find them here. Certainly no Galapagos vacation would be complete without a giant tortoise sighting!
So, keep reading to learn more about giant Galapagos tortoises. Where & when visitors can see them, how they have adapted and evolved to survive, plus lots of fun Galapagos tortoise facts and photos.
Galapagos Giant Tortoise Evolution
The Galapagos tortoise is known to have originally descended from the Chaco tortoise, a regular sized species from Argentina and Paraguay. But that is just a small part of the evolutionary puzzle. Ask yourself this: how did the Chaco Tortoise arrive to volcanic islands over 1000km away from mainland South America? Why did the tortoises then become so large in size? How did they evolve into the different subspecies that we find today?
Let’s start from the beginning. Between 2 and 3 million years ago the Chaco tortoise made an epic journey across the Pacific ocean. Perhaps some fell into a river, or were washed in by flash floods, either way they followed the river currents out into open ocean. Tortoises are surprisingly bouyant in water – they float like corks. So they could have bobbed along themselves, or survived on floating foliage. Tortoises can survive up to 1 year without food or water so their adventure would pose no immediate threat to their survival. Ocean currents from South America converge conveniently at the Galapagos islands, so it is in fact quite logical that they should eventually wash up on Galapagos shores.
Now, imagine that different tortoises washed up at different islands, each with distinct food sources and habitats. On one island the tortoises find lush green highlands with mud pools and plentiful ground level food sources. On another island less fortunate tortoises find a more arid habitat with scarce food and a tougher challenge to survive.
It is at this point that the story starts to get more interesting as natural selection comes into play. On the first island, the tortoises can eat freely and easily. Their dome shaped shell is no hinderance to survival because they can eat ground level plants that are everywhere. Life is a breeze.
Meanwhile life on the other arid island is much tougher. The tortoises here can only survive by reaching cactus fruits and pads that are almost out of their reach. Some of the tortoises naturally perish, while only those with a long neck and slightly curved shell at the front can survive by reaching food. The survivors all have this same particular shell and neck trait. So when they mate they are likely to pass those same physical traits onto their hatchlings. Now fast forward hundreds of thousands of breeding generations. The advantageous shell curve and neck length have been passed down to young tortoises many thousands of times. Each time the shell curve is enhanced slightly more to further enhance survival chances.
Eventually as you can see, we have two very different tortoise populations on the different islands. Dome shaped shells continue to dominate where ground food is abundant. While curved shells shaped rather like a saddle have become the norm on the arid island. The tortoise populations on each island are now sufficiently different in appearance and behavior that they can be recognised as seperate species. This is a great example of species evolution in action. A species will adapt over time to local habitat and environmental conditions, where useful genes and traits are passed down by survivors, maximising the chance of future species survival.
If we extrapolate our example to include all of the different islands at the Galapagos archipelago, we can understand how 15 different Galapagos tortoise species evolved over time.
Of course it still doesn’t answer our final question – how and why did the Galapagos tortoise grow so large? Scientists believe that this is due to the process of island gigantism. Simply put creatures that live in isolated locations with ample food sources and no predators are able to grow to larger sizes than they would be able to in their regular, more constrained environment.
How to see Galapagos Tortoises?
Today the Galapagos giant tortoise population size is estimated at between 15 and 20 thousand individuals, split over different islands.
The easiest way to see them is in captivity at tortoise breeding centers on Santa Cruz, Isabela or San Cristobal islands. The most famous center is the Charles Darwin Research Station in Puerto Ayora. These centers play a vital role in tortoise conservation, protecting eggs and hatchlings from predation by introduced species like dogs, cats, pigs and rats. Adult tortoises have no natural predators, so once the babies grow big enough they are released into the wild. Visitors can see the complete tortoise life cycle in action – from incubating eggs, to tiny babies, energetic adolescents, and large adults who drive the breeding cycle.
Visitors can also observe giant tortoises in their natural habitat. Highland ranches like El Chato are home to tortoise populations that roam freely in dense vegetation, with mud pools to cool off in. San Cristobal's Galapaguera center offers the best of both worlds - with giant tortoises roaming a large area, and babies kept in safe captivity.
When is the best time to see Galapagos tortoises?
The good news is that they can be spotted all year round. In terms of behavior, mating season is usually in the dry season (June to November) in the highlands, while eggs are laid in the lowlands during wet season (January to April).
Whether you see tortoises at a breeding center or in the wild, you will be able to clearly observe the contrasting shell shapes between species. Of course your naturalist guide will be happy to identify sub-species correctly for you, and explain their adaptations in more details.
For more information about Galapagos Tours to see giant tortoises first hand (as well as many other fascinating bird and mammal species), Contact a member of our team or call our toll-free numbers.
The 15 Different Galapagos Tortoise Species
In total 15 different Galapagos giant tortoise species have been identified, all from the genus Chelonidis. Each species population lived in a unique place from one another – either on different islands, or in the case of Isabela island populations were seperated by unpassable lava flows. In general terms the species fall into 3 types of Galapagos tortoise shell: Saddle-back, Dome and Intermediate.
Today 12 of the 15 species are still alive and well at the Galapagos islands. These are native to: Española, Fernandina, Santa Cruz (2 species), Santiago, Pinzon, San Cristobal and Isabela (5 species on each of Wolf, Darwin, Alcedo, Sierra Negra and Cerro Azul volcanoes).
3 species have unfortunately already become extinct - those from Floreana, Santa Fe and Pinta islands. Giant tortoises were long thought to be extinct on Fernandina too, until a single female (named Fernanda) was discovered there in 2019. Subsequent scientific tests have proven Fernanda to be the first Chelonoidis phantasticus (Fantastic Giant Tortoise) sighted since 1906. The race is now on to see if more of her species have been roaming a solitary life in remote areas of Fernandina; the ultimate goal would be to set up a breeding program to rescue this species. This echoes the story of Lonesome George, the last surviving Pinta tortoise who was discovered all alone in 1971, but sadly passed away in 2012 as last in his line.
So, as you can see, the Galapagos islands still hold many secrets, and the giant tortoise extinction list is not completely carved in stone.
Galapagos Tortoise Conservation
Giant tortoise conservation is a hot topic at Galapagos. Of course nobody wants to see further species extinction, yet today we find 6 species critically endangered, 3 endangered, and 3 vulnerable on the IUCN Red List.
In the past it was whalers and pirates who depleted tortoise numbers for food. Population numbers declined from over 250,000 back in the 16th century, to just 3000. Floreana was a particularly popular stopping off point for ships due to the island’s source of fresh water. Whalers would also stock up on tortoise meat and oil for their onward voyages, resulting in the complete extinction of the Floreana giant tortoise.
Today the surviving Galapagos tortoise species face very different threats. Invasive species introduced by humans (cats, dogs, pigs, goats, rats) destroy nesting sites, and eat eggs or baby tortoises. This combined with habitat destruction puts tortoise populations under severe stress.
Eggs and hatchlings are in particular need of a helping hand. At tortoise breeding centers, tortoises are raised in captivity, keeping them safe until large enough to defend themselves from predation in the wild. These projects have impressive success rates, and are key to the future of Galapagos tortoise populations.
Perhaps the best known success story is that of Diego. When the Española (Hood) tortoise population dropped to just 15 individuals it became clear that the species was in trouble. So Diego, a healthy adult who had been living at San Diego zoo, was shipped back to Galapagos with a very important job to do. Diego became a famous stud tortoise, fathering over 800 baby hatchlings with Española females. All have since been released onto Española island to repopulate and save their species from extinction. Finally in 2019 Diego was also released back onto his original birthplace island, to enjoy a well deserved retirement rest surrounded by his kids and grandkids.
In other important projects, the Galapagos Conservancy also support the control of invasive species, habitat recovery and mitigation of potential human-tortoise conflict.
Everything you ever wanted to know about the Galapagos Tortoise
How long does a Galapagos Tortoise live?
Galapagos Tortoise lifespan varies - they often live past 100 years in the wild, or to as much as 170 years in captivity. The age of an individual tortoise can be estimated by counting the rings of a shell scute.
How much does a Galapagos Tortoise weigh?
The giant tortoises found at Galapagos are the heaviest living species of tortoise on the planet. The largest recorded individuals weigh in over 400kg (880 lb), and can reach impressive lengths of close to 2 meters (6 ft).
What do Galapagos Tortoises eat?
Like all tortoises species they are herbivores, consuming a diet of cactus fruit or pads, grass, leaves, lichen, wild berries or other fruits. At Galapagos they are also able to digest poison apples. Giant tortoises receive most of their moisture from dew and plant sap, which they can store in their bodies for long periods of time, helping them to survive dry periods.
Giant Tortoise Habitat
Galapagos tortoises prefer the lush and cool highlands, surrounded by green vegetation, and close to mud pools. As cold-blooded creatures they bask in the early morning sun to warm up, and cool off in mud pools around midday. Giant tortoises only migrate down to coastal regions to lay eggs during the wet season. They use the same migration paths generation after generation, along well-defined tortoise highways.
Galapagos Giant Tortoise Reproduction
Galapagos tortoise mating is a surprisingly aggressive affair. Adult males will fight one another for dominance of females, stretching out their necks and even rising up on hind legs to gain height over rivals. After much hissing and occasional biting the winner is defined by the highest held head. The victor then enjoys the spoils, mating with his female(s) of choice amidst much crunching of shells and loud groaning. It can be quite a spectacle to behold.
Pregnant females journey several miles down to nesting sites on the coastal plains. This migration takes place in the wet season when the plains are green with vegetation. A deep nest is dug into sandy soil, and as many as 4 clutches of 12-16 eggs can be laid each season. Job done, the adults migrate back up to the cooler highlands.
Galapagos tortoise babies emerge from their nest after 4 to 8 months, instinctively digging their way to the surface. Their first 10-15 years of life are spent in the same lowland area of birth. These early years carry many risks for inexperienced tortoise hatchlings, who measure just 6cm long. Natural predators like the Galapagos hawk, and introduced species like pigs, rats and cats are always on the lookout for an easy meal. Sometimes tortoises will even fall into crevasses, or roll onto their backs and starve to death, unable to right themselves to escape. It is for this reason that the tortoise breeding centers lend a helping hand, gathering up eggs and incubating them in a safe environment.
Fun Giant Galapagos Tortoise Facts
• The Galapagos islands were originally named after the giant tortoise. Early Spanish sailors who landed at the archipelago spotted these unusual creatures, observing their strange saddle shaped shells. The old spanish word for saddle is Galapago, hence the islands were christianed Galapagos.
• Galapagos tortoises were taken aboard ships by pirates and whalers who used the islands to restock food and water supplies. Even Charles Darwin and his crew captured 30 live tortoises for this purpose, although he did also take 4 baby tortoises as pets.
• Galapagos tortoises share a symbiotic relationship with the Galapagos Finch. Finches crawl on and around tortoises, eating bugs and parasites. Both species benefit as the finch gets a tasty meal, and the tortoise is cleaned of irritating parasites.
• The gender of Galapagos tortoise babies depends on the heat of their eggs during incubation. Warmer temperatures produce female hatchlings (Hot babes), while cooler temperatures produce males (Cool dudes).
If you enjoyed this post, why not read more about other iconic Galapagos species: Darwin’s Finches and Galapagos Mockingbirds. We’ve also published more general blogs about Galapagos birds & Galapagos animals.
In Conclusion, the Galapagos tortoise is one of the biggest crowd pleasers at the islands. Truly no Galapagos visit would be complete without crossing their path. There is a big difference to seeing adults in the wild and babies in captivity, so try to include both into your trip itinerary. Above all spare a thought for those first Chaco tortoises that floated all the way out here. Imagine their incredible journey, and the new life they found on different islands. The giant Galapagos tortoise species that we find today certainly have a remarkable story of survival to tell.
