Galápagos tortoises

Common Name:
Galápagos Tortoise
Scientific Name:
Chelonoidis
Type:
Reptiles
Diet:
Herbivore
Size:
Up to six feet
Weight:
Up to 573 pounds
IUCN Red List Status:
Vulnerable
Current Population Trend:
Unknown

What is a Galápagos tortoise?

There are 13 living species of Galápagos tortoises, which are also sometimes called giant tortoises. These reptiles are among the longest-lived of all land vertebrates, averaging more than a hundred years. The oldest on record lived to be 175. They are also the world's largest tortoises, with some specimens exceeding five feet in length and reaching more than 500 pounds.

Giant tortoises were once so abundant on the Galápagos archipelago off Ecuador that the Spanish sailors who explored the region in 1535 named the string of islands for them. (The Spanish word for tortoise is galápago.) Although the islands were once thought to be home to at least 250,000 tortoises, only about 15,000 remain in the wild today.

Many of the tortoise's subspecies are listed by the International Union for Conservation of Nature as endangered or critically endangered. In 2012, the death of a beloved hundred-year-old giant tortoise named Lonesome George became a global symbol of the need to protect endangered species. As the last of his kind, Lonesome George’s death marked the extinction of the Pinta Island tortoise (Chelonoidis abingdonii).

However, conservation efforts have renewed hope for the survival of other giant tortoise species.  

Tortoise evolution and taxonomy

Scientists believe that Galápagos tortoises migrated from South America to the archipelago some two to three million years ago. By 1835, when Charles Darwin arrived for the expedition that would ultimately inspire his theory of natural selection, these tortoises had evolved into distinct yet closely related species. The similarities among the animals were so striking that scientists long debated whether they were actually different types of the same species.

Now, however, the scientific community generally accepts that there are 13 living species of Galápagos tortoise. One of them, Chelonoidis donfaustoi, was not identified until 2015, when researchers determined that the tortoises on the island of Santa Cruz are in fact two separate species. At least two species have gone extinct.

Appearance, diet, and behavior

Giant tortoises have thick legs and small air chambers inside their shells that help hold up their massive bodies. There are two main types: domed tortoises, which live in the cooler regions of the archipelago, and saddle-backed tortoises, which live in dry, coastal environments. Saddleback shells have a flared front opening that allows the animals to extend their necks to reach tall cacti.

Galápagos tortoises lead an uncomplicated life, grazing on grass, leaves, and cactus, basking in the sun, and resting for nearly 16 hours per day. A slow metabolism and an ability to store large amounts of water mean they can survive up to a year without eating or drinking. Galápagos tortoises play a key role in shaping their ecosystem by dispersing plant seeds in their dung.

Reproduction

Giant tortoises reach maturity at about 20 or 25 years old. They typically breed during the hot season, which occurs from January to May. Mating can take several hours, after which the female migrates to an area with dry, sandy ground. There, she digs a hole in which she lays two to 16 eggs. The eggs hatch after around 130 days, after which the young tortoises must dig their way up to the surface.

The temperature of the nest determines the young tortoise’s sex, with warmer nests tending to yield more females.

Threats to survival

Hunted as food by pirates, whalers, and traders from the 17th through the 19th centuries, between 100,000 and 200,000 Galápagos tortoises are estimated to have been killed off. Tortoises were also hunted for their oil, which was used to power lamps.

Today, non-native species that settlers introduced to the islands—including feral pigs, dogs, cats, rats, goats, and donkeys—are a persistent threat, preying on tortoise eggs and hatchlings and competing with giant tortoises for food.

Conservation

Galápagos tortoises are protected by Ecuadorian law and under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which prohibits all international trade. In 1959, the Ecuadorian government created Galápagos National Park to protect the tortoises’ habitat.

Captive breeding efforts in the Galápagos are yielding positive results. The Galápagos Conservancy has raised more than 7,000 tortoises of various species in captivity and released all of them into the wild. Chelonoidis hoodensis, a species from Española Island, has grown from a population of just 14 tortoises to more than a thousand.

In 2021, scientists confirmed the 2019 discovery of a Fernandina giant tortoise (Chelonoidis phantastica), a species previously thought to be extinct. The single female tortoise, found on its namesake Fernandina Island, has been taken to a breeding center. Researchers have also found tortoise tracks that could signal the presence of more C. phantastica individuals.


Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet