Irregular Webcomic! #3100

On my recent trip to South America, I was lucky enough to cruise around some of the Galapagos Islands. While there I saw several interesting things, including lots of wildlife: sea lions, iguanas (both marine and land types), and many many birds of various species. The latter included several species of Charles Darwin's famous finches. I expected these to be colourful birds, with distinctive patterns, but was surprised to discover upon seeing them that they are extremely nondescript small grey-brown birds.

The saddest thing I saw there, however, was Lonesome George.

The giant Galapagos tortoises used to live on at least nine of the different islands in the Galapagos archipelago. From a single ancestral population, the tortoises have diversified and become adapted to the varying conditions on the different islands. Modern taxonomists are divided on whether the resulting populations are subspecies within a single species, or qualify as being separate species. Some of the different populations can hybridise successfully, while others appear to be non-viable when cross-bred. In evolutionary terms, the tortoises are near the cusp of separation into truly separate species.

In historical times, there were ten distinct subspecies (or species, depending on your point of view) of giant tortoise in the Galapagos. Hunting by colonists drastically reduced the populations, wiping out two of the subspecies, on two of the islands. Today, specimens of seven subspecies live wild on six of the islands.

If you're keeping count, you'll notice there's one species and one island still unaccounted for.

The island of Pinta is the northernmost of the large Galapagos Islands, with an area of about 60 square kilometres. (Darwin Island and Wolf Island lie further north, but are only about a square kilometre in size each.) Until 1972, Pinta supported the giant tortoise subspecies Chelonoidis nigra abingdoni. After 1972, there were, to the best of our knowledge, no more giant tortoises on Pinta.

The last known specimen did not die in 1972. He was captured and transported to the Charles Darwin Research Station on the island of Santa Cruz. He'd been discovered the previous year, amidst a devastated ecosystem in which the plants the tortoises lived off had been decimated by feral goats. Researchers removed the tortoise for its own safety, and in an attempt to breed him to preserve the subspecies. Unfortunately, look as they might, the researchers couldn't find a female tortoise anywhere on Pinta Island, nor any other living specimens at all.

Over the following years, the male Pinta tortoise was kept with females of various other of the Galapagos tortoise subspecies. These females produced eggs on a number of occasions, but they have never been viable - not one has hatched. The Charles Darwin Research Station offered a US$10,000 reward for anyone who could bring them a female Pinta tortoise. The reward remained unclaimed.

The last Pinta tortoise became known as Lonesome George. Today, almost 40 years after his capture, he still lives at the Charles Darwin Research Station, penned with females of other subspecies in a desperate attempt to preserve his lineage and his subspecies. George is estimated to be 70 to 80 years old now, and is in good health and expected to live perhaps another 70 or 80 years.

It's possible there is another Pinta tortoise out there in the wild somewhere. In fact there is some genetic evidence that a specimen has been alive and interbreeding with tortoises on the nearby island of Isabela in the past few years. But unless such an individual is found and united with George (and turns out to be a female), George will probably be the last of his kind.