The evolution of extinction

When you think of Galapagos, the first two thoughts that come to mind are Charles Darwin and the giant tortoises. The giant tortoise is the iconic symbol of these islands. The name Galapagos comes from a Spanish word for saddle, in reference to the carapace of these gentle giants. The national park uses an image of the giant tortoise as its logo. Every time you view information about the Galapagos, you see images of the beloved giant tortoise.

The largest tortoises in the world, the Galapagos tortoises, have a long lifespan of 150 years. Male tortoises have been known to grow to over 600 pounds. The archipelago was never attached to a continent and all the plants and animals that reached the Galapagos did so by swimming, flying or floating. The journey across the ocean was too difficult for the grazing mammals that dominate the grasslands of other parts of the world, and thus the slow-moving tortoise reigned as king for thousands of years.

At the time of Charles Darwin’s visit in 1835, 250,000 tortoises and 12 subspecies were thought to exist here. It was the local lieutenant governor’s comments about tortoises that Darwin first dismissed, later to inspire him:

“I have not yet noticed by far the most remarkable feature in the natural history of this archipelago; it is that the different islands are, to a great extent, inhabited by a different set of beings. My attention was first drawn to this fact by the Lieutenant Governor, Mr. Lawson, stating that the tortoises differed from the different islands, and that he could say with certainty from which island each was brought in. For some time I did not pay sufficient attention to this statement, and had already mixed the collections of two of the islands.I never dreamed that islands, some fifty or sixty miles apart, and most of them in sight of one another, formed of precisely the same rocks, situated under quite a similar climate, rising to a height almost the same, they would have been rented differently, but we will soon see that this is the case.It is the destination of most travellers, as soon as they discover what is most interesting in any locality, they are apr cured; but perhaps I should be thankful that I have obtained sufficient materials to establish this most remarkable fact in the distribution of organic beings.”

Darwin and his companions aboard the Beagle viewed tortoises in the same way as pirates and whalers, tortoises were something to be exploited. Members of the Beagle collected 30 tortoises from the islands, which they ate on the way home.

In recent centuries, the systematic capture of turtles for meat and oil, as well as the introduction of new species, reduced the population by 90% compared to what it was during Darwin’s visit. Both the Floreana and Pinta tortoises are considered extinct and the remaining 10 species of Galapagos tortoises are listed as endangered species.

In 1959, 100 years after Darwin’s Origin of Species was first published, the Galapagos Islands became a national park. The park service in conjunction with the Darwin Foundation has made remarkable strides over the past 50 years toward the preservation, conservation, and restoration of native species.

Perhaps the best example of their efforts is the story of the Spanish tortoise. There was a time when there were at least 3,000 native tortoises on the island of Española. However, Española is one of the flattest and most accessible islands, making it a favorite spot for passing ships. As a result, in 1965 there were only 14 tortoises left living on Española: 2 males and 12 females. The tortoises were transferred to the Charles Darwin Research Station in Santa Cruz. A third male was then discovered at the San Diego Zoo. In the 1970s the tortoise breeding program began. From the brink of extinction, out of 15 tortoises, the program has been a success and today almost 1,500 Spanish tortoises have been repatriated to their native island.

With the success of the Española program, stopping the extinction of other species proved more problematic. In 1971, Lonesome George was discovered in the Pinta. He has the unique distinction of being the last remaining of his kind. George was relocated to Darwin Station and scientists began to work on the question of how to prevent the painted turtle from becoming extinct. Two females from Wolf Volcano on Isabela were pinned with George. These females were selected because they were found to be the closest genetic relationship to George and although any offspring produced would not be full-blooded, the species would continue in some capacity.

For years, George showed little or no interest in these females. But in 2008, the national park announced that George’s two companions had laid eggs. The world was waiting for news if Pinta’s career had been saved. At the end of the year it was announced that none of the eggs were viable and the search for how to save the species continued.

In 1994, a team of Yale scientists began the process of genetics of Galapagos tortoises. The group went to Isabela and took blood samples from 27 tortoises that lived atop the Wolf Volcano. About 2,000 tortoises are believed to live in and around Wolf. These tortoises are of great interest, as the tortoises here resemble more than one subspecies. Typically, each group of tortoises will either have a dome-shaped shell (similar to tortoises from Alcedo or other parts of Isabela) or a saddle-shaped shell (similar to Lonesome George) depending on the environment they live in. However, near Wolf, tortoises with domed and saddle-shaped shells can be found.

Over the next decade, the genetics team began collecting DNA samples from tortoises not only on Isabela, but also began taking samples from tortoises at Darwin Station, around the Galapagos, and captive tortoises around the world. At Pinta they found they took DNA samples from the remains of 15 tortoises and cataloged the information to gain a better understanding of the species.

When they started going through their database, the impossible seemed possible. They first believe they have discovered a second pure-blooded Pinta tortoise. A tortoise known as Tony, believed to be approximately 50 years old, lives in the Prague Zoo; based on all current data, Tony appears to be of the exact same subspecies as George.

While reviewing the DNA information, they discovered the reason why the wolf turtles seemed to resemble more than one subspecies. Isabela and the area near the Wolf Volcano used to be the last stop for pirate ships in Galapagos. It appears that these ships collected turtles on other islands during their stay only to discard them here. Upon analysis of the DNA samples, it was discovered that several of the tortoises living at Wolf were first-generation hybrid Pinta tortoises: tortoises born to Isabela mothers and Pinta fathers. This discovery meant that some of the tortoises living on Wolf were 50% of the same genetic subspecies as Lonesome George. This information provided new hope that through further research a pure-blooded or mixed-blood female Pinta tortoise may be found, and the Pinta breed may survive.

The genetic team seemed to have discovered a miracle; there were still more surprises to discover. The research uncovered descendants of the extinct Floreana tortoise. The Floreana subspecies became extinct in the early 20th century due to human activities, and unlike Lonesome George, no known example is known to have survived. However, DNA research discovered 9 tortoises with a high percentage of the Floreana genome (up to 94%) and they believe that 1 tortoise may even be pure blood. Of the tortoises identified as Floreana’s, 6 are female and 3 are male, all of which currently reside at the breeding center in Santa Cruz.

Building on the success of the Española breeding program, these new findings from the Genetics team, man can now make up for some of his earlier misdeeds. What was once extinct may not be so in the future. Everything is a matter of time with the help of science and mother nature.