Galápagos giant tortoises
What is a Galápagos giant tortoise?
Galápagos giant tortoises are ancient reptiles that have inhabited the Galápagos Islands for over two million years. In that time, these tortoises have evolved into over a dozen distinct subspecies suited to the different environments on each island. For example, saddleback tortoises have flared front shells that let them reach tall cacti in dry coastal areas, while domed tortoises live in misty highland forests and have more rounded exteriors.
Galápagos giant tortoises are the largest living species of tortoise in the world. These gentle giants can grow over 1.3 metres long (4.2 feet) from head to tail and weigh a hefty 300 kilograms (over 660 pounds). They also have a very slow metabolism, which allows them to survive over a year without food or water and live very long lives. The oldest Galápagos tortoise on record was thought to be 175 years old.
Protecting giant tortoises is essential to preserve the unique biodiversity of the Galápagos, as they play a primary role in the islands’ ecosystems. As herbivores, they disperse seeds and keep vegetation in check, while their nesting habits create pathways, wallows, and nest sites used by other animals. The tortoise’s large size and long lifespan make it a keystone species—meaning their ecosystem depends on them to function effectively.
Sadly, though, almost all subspecies of Galápagos giant tortoise are endangered. Centuries of exploitation by humans caused populations to plummet from over 250,000 to just 15,000 today. Ongoing threats like poaching, habitat loss, and invasive species also continue to put pressure on these animals.
What is a giant tortoise’s scientific name?
The scientific name for the genus of giant tortoises is Chelonoidis. There are over a dozen subspecies, each with their own name.
Some researchers have classified each type of giant tortoise as distinct species rather than subspecies. As of 2021, the most recent study once again suggests that all Galápagos giant tortoises belong to the same species, Chelonoidis niger.
Here is a list of the 12 currently surviving subspecies of the Galápagos giant tortoise:
- Volcán Wolf tortoise (Chelonoidis niger becki)
- Chatham Island tortoise (Chelonoidis niger chathamensis)
- Santiago Island giant tortoise (Chelonoidis niger darwini)
- Eastern Santa Cruz Island tortoise (Chelonoidis niger donfaustoi)
- Duncan Island tortoise (Chelonoidis niger duncanensis)
- Sierra Negra giant tortoise (Chelonoidis niger guentheri)
- Hood Island tortoise (Chelonoidis niger hoodensis)
- Volcán Darwin tortoise (Chelonoidis niger microphyes)
- Fernandina Island tortoise (Chelonoidis niger phantasticus)
- Western Santa Cruz Island tortoise (Chelonoidis niger porteri)
- Volcán Alcedo tortoise (Chelonoidis niger vandenburghi)
- Iguana Cove tortoise (Chelonoidis niger vicina)
Are giant tortoises endangered?
Yes, most subspecies of the giant tortoise are classified as endangered. Sadly, the Pinta Island tortoise (also known as the Abingdon Island tortoise), and Floreana Island giant tortoise are already extinct.
The Volcán Wolf tortoise, Volcán Alcedo tortoise, and Duncan Island tortoise are listed as vulnerable.
The Chatham Island tortoise, Iguana Cove tortoise, and Volcán Darwin tortoise are listed as endangered.
The Santiago Island giant tortoise, Sierra Negra giant tortoise, Fernandina Island tortoise, Western Santa Cruz Island tortoise, Hood Island tortoise, and Eastern Santa Cruz Island tortoise are classed as critically endangered.
The Galápagos tortoise was once an abundant creature on the islands. In fact, the name ‘Galápagos’ translates to tortoise, showcasing how common these reptiles once were in the region.
Unfortunately, centuries of exploitation for food and oil caused populations to reduce drastically. The main threats tortoises face today are poaching, habitat loss from agriculture, and competition from invasive species. Protecting the remaining tortoises is crucial to their survival.
Where do giant tortoises live?
Giant tortoises live exclusively on the Galápagos Islands, 1,000 kilometres (over 600 miles) off the coast of Ecuador in South America. Scientists believe the tortoises arrived from mainland South America by drifting on ocean currents millions of years ago before Darwin’s expeditions. As each island has a distinct habitat, the tortoises evolved into different subspecies with adaptations to help them thrive in their unique environments.
There are two main tortoise habitats. Saddleback tortoises—which have flared front shells to reach tall cacti and other food sources—live in the arid coastal regions.
Domed tortoises—which have more rounded shells—live in misty highland forests up to 2,000 metres (6,560 feet) above sea level.
Despite their adaptations, tortoises migrate between the highlands and lowlands for food.
Giant tortoises have faced severe threats from humans for centuries, causing populations to plummet. Ongoing threats like poaching, habitat destruction, and competition from invasive species continue to endanger the remaining Galápagos giant tortoises today.
Mass hunting from the 17th to 19th Century
From the 1600s to the 1800s, whalers and fur sealers hunted giant tortoises for their meat, as a live tortoise could provide fresh meat on board a ship for months without requiring food or water. These seamen took 100,000 to 200,000 tortoises during this period, splitting and drying the meat into ‘tortoise bread’ for long voyages or rendering fat by suspending tortoises over fires. They also exploited tortoise oil to fuel lamps. Such industrial-scale hunting devastated tortoise populations across the islands.
Continued illegal poaching
Though Ecuadorian law states that poaching a giant tortoise could net the assailant three years in prison, giant tortoises are still hunted today. They are targeted for their meat or to sell illegally as pets.
Recently, island officials found four slaughtered tortoises that had been hunted for their meat and sold on the black market. Rangers also occasionally find tortoise shells and bones hidden amongst vegetation, sad evidence of this furtive trade.
Park staff work tirelessly to intercept poachers and disrupt their activities through foot patrols and public tip lines. They also strive to shift community attitudes against poaching by emphasising protection and pride in local wildlife.
Habitat loss from agriculture and development
As the human population expands in the Galápagos, tortoise habitat is increasingly converted into farmland and towns. New fences and roads block tortoises’ traditional migration routes, forcing them to use other paths, where they are sometimes hit by cars when crossing roads.
Balancing development with tortoise conservation is an ongoing challenge across the Galápagos. While local communities need space to grow crops and expand infrastructure, this should not come entirely at the expense of native wildlife. Responsible planning that preserves vital tortoise migration corridors and nesting areas is essential.
Invasive plant species
Humans introduced aggressive, non-native plants like blackberry and supirosa to the Galápagos. These invasive thickets now dominate much of the tortoises’ habitat, obstructing their movement between lowlands and highlands.
To reduce the number of invasive plants, environmental officials use chemicals and manual removal processes while local community groups organise volunteer weed-pulling days. This level of ongoing control is needed to prevent reinvasion and keep key areas—particularly nesting grounds and migration routes—clear for tortoises to pass through.
Invasive animal species
The introduction of non-native animal species—including pigs, goats, cats, dogs, and rats—also threatens tortoises. They prey on eggs and hatchlings, attack adults, and compete with tortoises for food and resources. Controlling invasive species is crucial for tortoise conservation.
Eradication programs have successfully removed goats, pigs, and rats from some islands, while intensive hunting and sterilisation have helped suppress populations on others. However, constant vigilance is needed, as passing ships can reintroduce invasive species or bring new ones to the Galápagos.
Giant tortoises are ancient reptiles that have inhabited the Galápagos Islands for over two million years. Here are answers to some common questions about these iconic giants.
How long do giant tortoises live?
Giant tortoises typically live for over 100 years thanks to their slow metabolic rate.
The oldest known giant tortoise—affectionately nicknamed ‘Old Tom’—lived to the ripe old age of 175 and was born around 1750. He was said to have been collected as a young adult from the Galápagos Islands by Charles Darwin aboard the HMS Beagle in 1835. Tom lived the rest of his long life in the Australia Zoo until he died in 1926.
Where are giant tortoises found?
Giant tortoises live exclusively on the Galápagos Islands off the coast of Ecuador. Scientists believe they arrived from mainland South America over two to three million years ago by drifting on ocean currents. Once on the islands, they evolved into over a dozen different subspecies.
The Galápagos Islands, where giant tortoises roam, sit directly on the Equator about 1,000 kilometres (over 600 miles) off the west coast of Ecuador. The cool, nutrient-rich waters of the Cromwell Current help create a unique ecosystem. The 13 major islands and over 100 smaller islets each have their distinct habitats and types of tortoises.
Are giant tortoises reptiles?
Yes, giant tortoises are reptiles, members of the class Reptilia. They belong to the scientific order Testudines, which includes all turtles and tortoises. These ancient creatures are among the longest-lived land vertebrates.
As reptiles, giant tortoises are cold-blooded and lay eggs on land rather than giving live birth. Baby tortoises hatch independently and receive no maternal care. Reptiles have scales rather than hair or feathers, breathe air, and are ectotherms (or cold-blooded), meaning they use external heat to regulate their body temperature.
How do giant tortoises mate?
Giant tortoises reach sexual maturity between 20 and 25 years old, and the mating season lasts from January to May (during the hot season). Mating rituals take several hours, after which females migrate to sandy nesting areas to lay 2 to 16 eggs in a buried clutch. After 130 days of incubation, the hatchlings dig their way to the surface and find their way to the sea. They never receive direct care from their parents.
Interestingly, the temperature of the nest determines the sex of the hatchlings, with warmer nests yielding more female tortoises.
What do giant tortoises eat?
Giant tortoises are herbivores that graze on grasses, leaves, cacti, and other vegetation. Thanks to their slow metabolism, giant tortoises can survive over a year without food or water.
Can giant tortoises swim?
Giant tortoises cannot swim today. However, scientists believe ancient tortoises may have floated from South America to the Galápagos Islands on ocean currents over two to three million years ago. Since then, though, their shells have become more domed as a result of being isolated on the islands, removing their ability to swim.
Do giant tortoises have predators?
The only native predator of giant tortoises is the Galápagos hawk, which eats eggs and hatchlings. However, invasive species harm tortoises, including rats, pigs, ants, dogs, and cats. Humans have also overhunted tortoises for centuries.
Do giant tortoises hibernate?
No, giant tortoises do not hibernate. The Galápagos Islands have warm, stable temperatures year-round due to their equatorial location. Therefore, tortoises remain active all year and do not need to hibernate through colder months.
How big are Galápagos giant tortoises?
Giant tortoises can grow over 1.3 metres (4.2 feet) long from head to tail and weigh up to 300 kilograms (over 660 pounds). Their gigantic size results from a lack of natural predators on the islands, allowing them to evolve to their maximum size.
How heavy are giant tortoises?
Adult giant tortoises weigh between 90 and 300 kilograms (200 to 660 pounds). The heaviest recorded tortoise weighed in at 304 kilograms (670 pounds). It is their slow metabolic rate that allows them to grow to such a large size.
Are giant tortoises dangerous?
No, giant tortoises are not dangerous to humans. They are docile, gentle herbivores. Instead, it is humans who are dangerous to giant tortoises. Years of overhunting and habitat loss are threatening their survival.
Despite their gentle nature, giant tortoises shouldn’t be approached. In fact, it is illegal to approach or interfere with giant tortoises in the wild.
Can I have a giant tortoise as a pet?
No, keeping giant tortoises as exotic pets is cruel and illegal. They have complex needs that are nearly impossible to meet in captivity. Instead of taking a tortoise from the wild, consider supporting reputable sanctuaries or donating to conservation organisations.
How many Galápagos giant tortoises are left?
Scientists estimate that around 15,000 giant tortoises remain in the wild across all islands and subspecies. However, some subspecies are very depleted, like the Fernandina tortoise, which has less than 10 individuals left.
How can I help save giant tortoises?
Giant tortoises represent a crucial piece of the unique evolutionary puzzle across the Galápagos Islands. They have inhabited the archipelago far longer than humans and play an integral role in island ecology.
Though centuries of exploitation followed by ongoing threats leave giant tortoise populations decimated and endangered, it is not too late to reverse their declining numbers. Through anti-poaching enforcement, habitat protection, invasive species control, and climate-wise conservation, we can help protect giant tortoises. Focusing conservation efforts on these flagship species will help preserve the delicate interplay of life found nowhere else on Earth.
How can you help?
Anti-poaching enforcement, habitat protection, invasive species control, and climate-smart conservation all help protect Galápagos giant tortoises, which are vital to their ecosystems.