darwin riding a tortoise

If there is one animal that has come to symbolize the Galapagos Islands, it is the giant tortoise. You’ll find its likeness in the logos of the Galapagos National Park, the Charles Darwin Foundation, and the Galapagos Conservancy.  In fact, the word ‘Galapagos’ itself is derived from an Old Spanish word for saddle, in reference to the shape of some giant tortoises’ shells, which vary between the different 15 subspecies (four of which are now extinct) found throughout the islands. Darwin’s observations of these variations would eventually play a significant role in the development of his theory of evolution by natural selection. In addition to playing a critical role in shaping Darwin’s big idea, the Galapagos giant tortoise is fascinating in its own right. Here are a few reasons why:

1. They are one of the great Galapagos conservation success stories.

It is believed that there were around 250,000 tortoises living in the Galapagos when the archipelago was discovered in the 16th century. By 1974 there were only about 3,000 individuals left in the wild. Three of the originally identified subspecies had become extinct and others were on the brink. Humans had slaughtered tens of thousands of tortoises for food and oil and introduced species such as ants, rats and pigs that devoured tortoise eggs and nestlings. Other introduced species, especially goats, destroyed the tortoises’ habitats and plundered their food. Captive breeding and release programs, which began in 1965, helped restore tortoise populations to healthier levels. And massive ecosystem restoration initiatives have eradicated some of the most harmful invasive species. Project Isabela, for example, which began in 1997 and was completed in 2006, employed helicopter-borne snipers to completely eliminate tens of thousands of goats from three islands. As a result of these efforts, tortoise populations have bounced back considerably. Today, it is estimated that there are 20,000 to 25,000 wild tortoises living in the islands.

 2. They are apparently (and unfortunately) delicious.

As I mentioned above, one of the reasons that tortoises nearly became extinct is that people really liked to eat them. Passing buccaneers and whalers often anchored in the Galapagos to load up on fresh tortoises, which, thanks to their remarkably slow metabolisms, could survive in a ship’s hold for up to two years without food or water. It wasn’t just the tortoise’s long shelf life that put it in jeopardy.  According to many historical accounts, they are also really, really tasty. Buccaneer William Damper wrote in 1697, “They are extraordinarily large and fat; and so sweet, that no pullet eats more sweetly.” And US Navy Captain Amasa Delano, who visited the islands in 1801, said, “their flesh, without exception, is of as sweet and pleasant flavor as any I ever eat.” Even Darwin got in on the act. While his accounts seem to indicate that he was generally indifferent to the taste of tortoise meat, he once admitted that, “young tortoises make capital soup.”

3. Though they are technically vegetarians, they may sometimes eat birds.

Tortoises are herbivores; their diets consist mainly of cacti, leaves, lichens and berries. But, according to the author of the book “Living Turtles of the World,” they have been observed killing and eating small birds. Here’s how it supposedly works: tortoises have a mutualistic relationship with some species of Galapagos finches and mockingbirds. A small group of birds will hop on the ground in front of a tortoise to indicate that they wish to clean it of parasites. In response, the tortoise will rise up and extend its neck and legs, which enables the birds to access its neck, rear legs, cloacal opening and skin. This would seem like a win-win situation – the birds get a free meal and the tortoise gets rid of annoying parasites. But sometimes, according to the book’s author, a bird wanders beneath the tortoise, which suddenly withdraws its arms and legs and collapses, killing the bird instantly. Then the tortoise steps back and eats its hapless victim.

4. Extinct tortoise species are still with us.

Thanks to extensive research into giant tortoise genetics, scientists have discovered that there are quite a few hybrid tortoises living in the Galapagos. Some of them, it turns out, are the direct descendants of now extinct lineages. On Isabela’s Wolf Volcano, for example, some individuals are clearly descended from the Floreana tortoise, which hasn’t been around for 150 years. And they’ve even discovered tortoises with a dash of Pinta tortoise genes. Lonesome George, the last Pinta Island tortoise, died in 2012 after forty years in captivity. Scientists believe that all of this hybridization is the result of the activities of buccaneers and whalers, who presumably moved tortoises between islands. It is significant because it could one day pave the way towards bringing back extinct tortoise subspecies.