A Galapagos Tortoise Weighs Almost 1,000 Pounds

Spanish explorers and cartographer Abraham Ortelius visited the islands in 1570. They were taken aback by the giant tortoise species and thought the unique shape of their shells resembled English saddles, or "galápagos" in Spanish.

The Galápagos tortoises left a big impression: Ortelius then used the name "Insulae of the Galapagos" in his atlas, thus naming the 10 islands after the now-iconic giant tortoises.

Galapagos tortoises are true giants of the reptile world, with adults weighing up to 900 pounds (408 kg) and measuring over 5 feet (1.5 meters) in length.

Their massive shells come in two main shapes: domed and saddlebacked. Domed tortoises with rounded shells are from cooler, wetter areas. They are typically found in the more humid islands of the Galapagos.

Saddlebacked shells with a raised front are found in the drier habitats of the arid islands, where tortoises need to stretch their necks to reach vegetation. The saddleback shells allow them to reach tall cacti.

These giant tortoises have thick, scaly legs and long, sturdy necks that help them forage. Juvenile tortoises are smaller versions of their adult counterparts, with softer shells that harden as they age. Their slow metabolism and strong build are perfectly suited for life on the Galápagos Islands.

The Galápagos Islands are home to multiple subspecies of giant tortoises, each adapted to its specific island.

Historically, there were 15 subspecies, but 12 are thought to still remain today. One of the most famous extinct subspecies is the Pinta Island tortoise, made famous by Lonesome George, the last known individual of his kind.

Tortoise populations vary widely depending on the island and habitat. For example, the largest populations are found on Isabela Island, while smaller groups inhabit islands like Española and Santiago.

Conservation efforts focus on preserving the genetic diversity of these giant tortoise species.

Galapagos giant tortoises are mostly solitary creatures, but they occasionally gather in groups, especially around waterholes or prime feeding spots. During the mating season, males compete for dominance, often clashing shells and ramming each other in displays of strength.

Despite their solitary nature, tortoise populations interact indirectly by maintaining pathways through dense vegetation. These pathways, formed over generations, benefit not only the tortoises but also other animals on the islands.

Galapagos giant tortoises are strict herbivores, feeding on a diet of grasses, leaves, cacti and fruit. Their long necks and high-domed shells help them reach food in their specific habitats. Saddlebacked tortoises, for instance, use their raised necks to access vegetation higher off the ground.

Galapagos giant tortoises spend hours each day foraging, taking advantage of the islands' rich seasonal vegetation.

Also, they can survive for up to a year without eating or drinking! Thanks to a slow metabolism, they are adept at storing fat and water in their bodies to endure dry seasons.

These tortoises are found across the Galápagos Islands, inhabiting a variety of environments from lush highlands to arid lowlands. Domed tortoises typically live in cooler, wetter areas with abundant vegetation, while saddlebacked tortoises thrive in hot, dry regions where food is scarcer.

Galapagos National Park, which protects much of the islands, is a vital haven as a tortoise habitat. Conservation centers like the Tortoise Center on Santa Cruz work to restore their habitats and support juvenile tortoises before releasing them into the wild.

The life cycle of a Galapagos tortoise begins when a female lays her tortoise eggs in a shallow nest, typically digging a hole in sandy or volcanic soil. Each clutch contains two to 16 eggs, which incubate for four to eight months. The temperature of the nest determines the sex of the hatchlings, with warmer nests producing females and cooler nests producing males.

Once the eggs hatch, newly hatched tortoises and young tortoises face numerous predators, including rats, cats and hawks. Juvenile tortoises grow slowly, reaching maturity around 20 to 25 years of age. Their slow development and long lifespan make them one of the longest-living vertebrates on the planet.

The Galapagos giant tortoise spends most of its time eating, bathing in water or simply relaxing during the day. This restful lifestyle could be a factor in its lengthy lifespan.

The Galapagos tortoise faces significant threats from a variety of predators, both natural and introduced. Historically, the tortoise's only natural predators were certain species of large birds and mammals, such as hawks and native land crabs, which would target tortoise eggs in the nesting areas.

However, with the arrival of humans and subsequently introduced species, the situation on the islands has worsened. While the tortoises themselves are large and capable of defending against many predators, their eggs and hatchlings are vulnerable.

Feral pigs, dogs, and farm animals like cattle and horses have caused severe damage to tortoise populations. Feral pigs are particularly destructive, as they root through the tortoises' nesting areas, consuming eggs and even attacking young tortoises. Similarly, feral dogs prey on smaller tortoises and can disrupt natural nests.

Invasive species such as rats also pose a danger to eggs, often raiding nests for food. Rats have been so populous on the island — wreaking havoc on the tortoise hatchlings and beyond — that environmentalists are exploring GMO rat DNA in the Galápagos Islands to reduce the rat population.

The continued survival of Galapagos tortoises depends heavily on efforts to control introduced species, protect nesting areas and ensure that natural predators are kept in balance, preventing the further decline of this iconic species.

The Galapagos giant tortoise of the archipelago has long been recognized as an endangered species due to a combination of factors, both natural and human-induced. These reptiles once thrived across the islands but have faced a dramatic decline in population since the arrival of humans and introduced species.

Post-Darwin Changes

Naturalist Charles Darwin, who visited the islands in 1835, famously noted the variations in tortoise species across the different islands, which helped him develop his theory of evolution by natural selection.

However, it wasn't long after Darwin's visit that human activities, such as hunting and the introduction of invasive species, began to push the tortoises to the brink of extinction.

Non-native Predators

The introduction of non-native predators, such as feral pigs, dogs and rats, has had a devastating effect on tortoise populations, particularly by targeting tortoise eggs in their nesting areas.

Farm animals, including cattle and horses, also damage tortoise habitats and nesting grounds, making survival increasingly difficult.

Breeding Programs

To protect these endangered creatures, the Charles Darwin Research Station on Santa Cruz Island has played a key role in conservation efforts, focusing on restoring tortoise populations.

The station runs a tortoise breeding program, where tortoises are carefully raised in captivity and then reintroduced into their natural habitats, particularly on islands where native species are better protected from introduced predators.

Rebalancing Ecosystems

Efforts to protect the Galapagos giant tortoise go beyond just breeding programs. Ecological restoration projects on islands like Santa Cruz are essential to controlling invasive species, protecting natural nesting areas, and restoring the balance of native ecosystems.

These initiatives also involve the eradication of feral predators and the restoration of natural habitats where tortoises can thrive undisturbed.

Through the combined efforts of conservationists, scientists and local communities, the future of the Galapagos giant tortoise looks more promising, though continued vigilance is required to ensure that this remarkable species remains a vital part of the islands' unique biodiversity.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.