But with the discovery of this new species, we probably also lost another giant tortoise species – paradoxically.

That can be read in the magazine heredity† The study relies heavily on work done by fellow researchers more than a century ago. Those fellow researchers had gone on an expedition to the Galapagos Island of San Cristóbal in 1906 and had collected the remains of several dead giant tortoises there. Those remains were in a cave on San Cristóbal; the tortoises must have died in that cave long before the expedition saw the light of day. Their remains – bones and shields – were collected and taken away in 1906. But the researchers didn’t just return in 1906 with the remains of dead turtles; they also brought a live specimen. Based on their finds, the scientists described a new giant tortoise species at the beginning of the last century that they named Chelonoidis chathamensis gifts. And it was assumed that these giant tortoises still live on San Cristóbal to this day and have been flourishing there again for half a century – thanks in part to a ban on poaching.

Fairy tale

But that turns out to be a fairy tale, researchers now write in the magazine heredity† After all, they once again examined the remains of the giant tortoises, which were found in 1906. The DNA of the turtles was also examined and compared with that of the giant tortoises that live on San Cristóbal today. And guess what? The genetic differences between the giant tortoises described in 1906 and the giant tortoises that live on Galapagos Island today are enormous. In fact, they are so large that the giant tortoises that live on the island today are not up to C. chathamensis can be counted, but deserve its own species name. In other words, the scientists have discovered a new giant tortoise species!

Not seen in 1906

It may seem surprising that these turtles have been scurrying around under the wrong name for over a century. But if you take a closer look at the research that has been done on these turtles, you will soon discover where exactly it went wrong. For example, in 1906 the researchers traveled to the southwestern part of San Cristóbal. There they found the remains and a live specimen of their new giant tortoise species. However, the expedition never visited the northeastern part of the island, which at the same time was home to giant tortoises that were genetically very different from C. chathamensis† And when later researchers did visit the northeastern part of the island and came across giant tortoises there, it was assumed that until that species discovered in 1906, they C. chathamensis belonged.

But that is not the case, scientists are now showing. And with that we now have a giant tortoise species richer. Although…not really. Because where in 1906 the researchers described a new giant tortoise species that lived on the southwestern part of the island, today no giant tortoises can be found on that part of the island. And with the discovery that the northeastern population belongs to a different species, it probably means that C. chathamensis is now extinct, scientists must now conclude. So we gain a living giant tortoise species, but at the same time – looking back somewhere in the middle of the twentieth century – we also lost one.

New name

As far as the researchers are concerned, the extinct species remains the name C. chathamensis and the population in the northeastern part of the island is given a new name. It is not yet clear what the ‘new’ giant tortoise species should be called.

Future research

Follow-up research should show to what extent the two giant tortoise species – which must have once inhabited San Cristóbal at the same time – are related. The researchers hope that this research will also clarify how the island obtained two giant tortoise species. It is possible that the species share an ancestor that arrived on the island long ago and spread there, after which the southwestern and northeastern parts may have been temporarily separated by rising sea levels and the populations on each of the two resulting sub-islands evolved into separate species.

Both species must have had a hard time at the beginning of the twentieth century. In the low-lying southwestern part of the island, C. chathamensis at loggerheads with settlers and whalers. Eventually, the population of giant tortoises there disappeared in the mid-twentieth century. And also in the higher northwestern part of the island, things did not go well with the giant tortoises in the mid-twentieth century – which at that time were therefore still regarded as C. chathamensis† Their numbers had fallen to about 600 copies, partly due to poaching. In the seventies there was a lot of action; poaching was curbed and goats – which prey on the tortoises to eat – were taken off the island. That approach worked. And now there are about 8,000 giant tortoises living on San Cristóbal, each of which – as we now know – belong to a species unknown to us until recently.