The life of Diego the giant tortoise

In 1934, scientists on a collecting expedition had removed Diego from his island, most likely while he was still a young tortoise, and ferried him and other live specimens to San Diego Zoo in California. It is a good thing that they did, for this tortoise ended up playing a crucial role in what conservation legend Linda Cayot described as “one of the most successful captive-breeding… programmes to recover an endangered species anywhere in the world.” Without him, it may not have been possible.

In the early 1960s, several years before the establishment of the Galapagos National Park Service, staff of the recently founded Charles Darwin Research Station surveyed Española for tortoises. They found a handful of survivors, but with their island decimated by invasive goats and no signs of the tortoises breeding, the decision was made to transport the remaining 14 giant tortoises – 12 females and two males – from Española to the outskirts of Puerto Ayora on Santa Cruz in the hope of establishing a captive breeding programme. The early years were fraught with challenges, but from 1971 onwards, some hatchlings survived.

When it became clear that San Diego Zoo had an Española tortoise from the 1930s expedition, it was agreed that he should be returned to Galapagos. So in 1977, after an absence of 43 years, this male returned to the Archipelago, although he would spend another 43 years in captivity on Santa Cruz, assisting in the recovery of his species. He was such an enthusiastic participant in the breeding programme that he was nicknamed ‘Macho’ for a time, before being renamed more appropriately as ‘Diego’. But he certainly was productive. A study published in 2004 revealed he had had offspring with nine of the 12 females and fathered almost 60% of all the captive-bred hatchlings.

By 1978, the Galapagos National Park had eradicated goats from Española, and between 1975 and 2012, they released 1,825 captive-born hatchlings onto the island. In the 1990s, there was evidence that the wild tortoises were successfully breeding and the current population size is estimated to be well over 2,000. Then, when the captive-breeding programme was wound up in 2020, the original 15 Española adults – Diego amongst them – were returned to their native island.

For Washington Tapia, who has borne witness to most of the conservation success stories of the last 35 years, releasing these tortoises was a poignant moment that brought him close to tears. “I considered each one a conservation hero, having saved their species,” he wrote. “I believe these tortoises knew they were home.” Diego has had an unusual life for a giant tortoise, travelling to the northern hemisphere to entertain and educate a North American zoo-going audience, dedicating over four decades to saving his species, before finding himself back where he began in the wilds of Española, living the giant tortoise dream. And all before his 100th birthday.