The Incredible Story Of How Giant Galapagos Tortoises Started Breeding Again After A 100-Year Absence

What is thought to be an image of a Pinzón (or Duncan) tortoise taken in 1846. Internet Archive Book Images/Flickr

Josh Davis 03 Jan 2018, 17:49

When researchers realized that none of the few remaining giant tortoises on the Galapagos Island of Pinzón were younger than 70 years old, they knew that something was seriously amiss.

It seemed that by the time scientists had cottoned on in 1965, not a single tortoise had survived from egg to adulthood in over half a century, and the cause was all down to mammalian invaders. It would not be for another 50 years that baby Pinzón tortoises would be seen wandering the island once more.

Like the majority of Galapagos giant tortoises, those that had been living in isolation on the volcanic island of Pinzón (also known as Duncan Island) in the heart of the archipelago were being threatened by introduced rats. The animals had been transported to the islands on the ships of whalers and traders, who would stop off en route across the Pacific.

With no natural predators and a voracious appetite, the number of rats scattered across the handful of islands rocketed to a shocking 180 million individuals. Quite unsurprisingly, the plague of rodents wreaked havoc, pushing many species found nowhere else on Earth over the edge of extinction, and many others pretty damn close.

By the time conservationists became aware of the scale and devastation of the problem that had swept across Pinzón Island in the 1960s, they found that there were only between 100 and 200 of the island's native giant tortoises left, and that worryingly none of these were under around 70 years in age. They concluded that the rats on the island had likely been feasting on the eggs of the tortoises, and any hatchlings that managed to survive the first onslaught, since at least the end of the 19th century.

By 1965 the decision was made to remove as many of the tortoises as possible to an external breeding center in order to give them a chance to breed, which despite their grand old age, they did rather well. Unfortunately, the birds that nest on Pinzón were also suffering.

Fast forward to 2012, and scientists were ready to attempt a dramatic approach to ridding the entire island of all rats by air dropping 20,000 kilograms (around 440,000 pounds) of poison designed to attract the rats, but repel any other wildlife that might accidentally eat it. Incredibly, it worked. 

A year later, and the team was finally able to give the Pinzón giant tortoise a homecoming, releasing 118 juveniles to join the last remaining members of the species still clinging on. Miraculously, within just two years the conservationists heard the pitter patter of tiny feet, and found the first baby Pinzón tortoises to have been born on the island for over a century.

Since then, not only are the giant reptiles still thriving but so is the host of other wildlife that has managed to recover on the island since the removal of the pesky rodent invaders.

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