The Galapagos Tortoises Reviving an Island’s Ecosystem

When English naturalist Charles Darwin first arrived in the Galapagos Islands in 1835, he noted the differences in giant tortoises from island to island. While some giant tortoises sported dome-shaped carapaces or ‘shields,’ were larger in size and featured shorter necks and limbs that evolved over centuries of foraging close to the ground, others were more saddleback, with a head and neck longer than that of others Galapagos species enabling them to reach higher growing plants. Each tortoise subspecies had evolved in isolation over thousands of years, adapting to their particular environment. 

Before humans came to the Galapagos, the archipelago’s Española Island was home to 8,000 or so of the Hood Island giant tortoise subspecies. As one of the smaller giant tortoise varieties, these ancient saddleback reptiles fed on cacti and leaves, roaming freely about the Galapagos’s southernmost island. However, by the mid-20th century, only 14 of the endemic creatures remained. Now, thanks to an extremely successful breeding program, these Galapagos giant tortoises are not only making a comeback but also reviving the island’s ecosystem. 

What is a Galapagos Giant Tortoise?

Giant tortoises arrived in the Galapagos Islands from South America’s mainland two to three million years ago and were able to grow so enormously because they had no natural predators. Today, the Galapagos giant tortoise is the largest living species of tortoise on Earth, with some specimens reaching more than five feet long and over 500 pounds. Its subspecies are native to seven islands in the Galapagos archipelago.

The Galapagos giant tortoise is a keystone species, meaning it plays a key role in keeping their ecosystem intact. Galapagos giant tortoises are remarkable seed dispersers, distributing large quantities of seeds in their feces as they travel over long distances and creating nutrient-rich water for plants and insects by relieving themselves in ponds. By trampling areas of vegetation as they move, it allows for new plants to grow. On Española Island, they’ve also historically maintained clearings for Galapagos waved albatrosses—white-headed avians with massive wing spans up to 6.6 feet across that need a running start for take-off. The island is the sole breeding ground for their entire population. 

Galapagos giant tortoises spend about 16 hours per day resting and the remaining hours snacking on grasses, fruits and cactus pads. As some of the longest-lived land vertebrates on the planet, their average age is more than 100 years old. 

Protecting a Species

Galapagos National Park was established in 1959 at the same time Española Island’s tortoises were on the brink of extinction. The Ecuadorian government created the park to protect its unique endemic wildlife, including marine iguanas, Galapagos hawks, and flightless cormorants, and to save the many creatures under threat from habitat loss, invasive species and over-exploitation. Whalers—and before them, pirates—had been hunting tortoises as food and later harvested them for oil. These sailors also left behind goats, which turned feral and began destroying the natural vegetation, eliminating both the tortoises’ shade and water supply and causing the population of tortoises—both on Española Island and across the archipelago—to plummet. 

A Tortoise Turning Point

But rather than allow these ancient reptiles to go extinct, scientists devised a plan. In 1965, the Charles Darwin Research Station (CDRS) and the Galapagos National Park Directorate (GNPD) established the islands’ first Tortoise Center. Its purpose: to breed and rear Galapagos giant tortoises in captivity to restore these threatened populations. Over the next decade, all 14 of Española Island’s remaining tortoises were successfully removed and relocated to the center on Santa Cruz Island—a tourist hub for the entire archipelago, ready to mate. Although they consisted of 12 female and two male tortoises in total, they wouldn’t be working alone. 

Meet Diego

Diego the giant tortoise had already spent 30 years living at the San Diego Zoo, beginning in the late 1940s, when DNA determined that this prolific breeder had originated on Española Island. Rather than continue his California lifestyle, Diego was sent back to the Galapagos to help save his species from extinction. For more than four decades, this ‘Casanova’ tortoise worked so tirelessly at his job that his love life became legendary. He fathered more than 900 Española Island offspring. He’s also over a century old. 

The End of a Breeding Era

Along with Diego and the other Española tortoises breeding in captivity, the island’s repatriated tortoises had begun mating as early as 1990. The number of Española tortoises had already increased to more than 2000 by the 2010s, so in 2019, Ecuador’s Ministry of Environment decided that Española’s tortoise population was ready to proliferate naturally. More than 55 years since the program’s inception, the captive breeding of Española tortoises officially stopped in January 2020. Then, just six months later, all 14 original tortoises—with Diego the ‘Cassanova’ in tow—were released back into the wild. 

Today, Española’s 23-square mile stretch of land is home to more than 3000 of these once-again, free-roaming giant reptiles—all of them the children and grandchildren of the original 15 tortoises. Their numbers continue to increase, and their presence is spurring biodiversity, including assisting with the return of open savannas and prickly pear cactus. The tortoises are fitted with microchips, allowing researchers to keep an eye on their health and survival. 

To see these remarkable Española Island creatures and hear their tale of recovery (the most significant population recovery of all Galapagos giant tortoise subspecies), book one of Nat Hab’s Galapagos “Eastern” itineraries. These extraordinary island-hopping adventures include a night at Nat Hab’s Tortoise Camp on Santa Cruz Island. Here, you can view the protected pens where other tortoise subspecies continue to breed and maybe even spot a tiny hatchling or two.