“Whatever happens to this single animal, let him always remind us that the fate of all living things on Earth is in human hands.”
– Wording on information panel beside Lonesome George’s pen
The last member of a species died this year. “Lonesome George” was the only Pinta tortoise left in the world.
Pinta is one of the Galapagos Islands. These islands are remote from the mainland of South America and far enough from one another so animals cannot interbreed. Separation over eons of time caused the development of distinct species on each of the islands. Perhaps the best known are finches.
HMS Beagle, on which Charles Darwin was the naturalist, made a stop on the Galapagos in 1835.
A careful observer, Darwin found that there were a variety of finches on the Galapagos archipelago. Each species had its own shaped beak, and the beaks were gradated from small to large. Beak size and shape varied by diet, which in turn was determined by the niche that the bird occupied. This range in size was a clue that lead Darwin to understand evolution.
The volcanic Galapagos are about 600 miles from the mainland of Ecuador and separated by up to 50 miles of open ocean from each other. If the islands were closer together, the birds could have easily flown from one to the other and interbred, and they probably would not have developed different niches and beaks. It is only a rare storm that carries the birds from one island to the next.
The Galapagos tortoises offer another example of speciation. They are huge, the largest weighing more than 800 pounds and having shells six feet long. They eat plants, including cacti – up to 80 pounds a day! – and can live more than 100 years. They have an interesting mutualism with some finches. The birds hop on the ground facing the tortoise, at which point the giant extends its neck and rises up on its legs. The birds will then groom the reptile.
These giant tortoises are not very good swimmers, which has contributed to developing at least 10 different varieties with significant differences. Whether the variations are great enough to be considered different species or just subspecies is not clear.
Galapagos males assert dominance over one another by seeing who can reach his head highest. A peaked shell differentiated the Pinta Island tortoises, allowing their necks to reach higher than other varieties.
The meat of these animals is reportedly tasty. Sailors collected them by the thousands in the 19th century, then turned them upside down and kept them as living larders on board ship. The tortoises could last for more than a year without food or water.
This careless harvesting probably killed off some varieties and has caused confusion for biologists who are trying to figure out what species lived where.
Goats were introduced to Pinta Island in 1958. They created havoc by eating much of the food that tortoises like, further jeopardizing the reptiles. It took years to eradicate these hungry mammals.
The last known Pinta Island tortoise was found in 1971 and taken to the Charles Darwin Research Station on the Islands, where he attracted tens of thousands of visitors. Nicknamed “Lonesome George,” he was already mature, so there is no way of telling how old he was.
Several expeditions combed Pinta for other members of the species. They found several skeletons but no live animal, and no sign of an animal that might have been recently alive. Lonesome George was unique.
In an effort to preserve at least part of his genetic pedigree, females of other tortoise subspecies were introduced. Unfortunately, Lonesome George never took much of a liking to them and there were no offspring. There had been thoughts of trying to preserve his lineage in other ways such as in vitro fertilization, but that wasn’t practical.
Lonesome George was found dead on June 24. His was the 802nd known species (or subspecies) to be driven extinct in the last 500 years; almost all these extinctions have had a human cause. The government of Ecuador had made every effort to protect George’s life and preserve the Pinta species. This effort was appropriate for the first country in the world to recognize the rights of nature.
George was lucky in that he belonged to a species that was recognized as being at risk of extinction.
Biologists suspect that thousands of species go extinct every year without ever being described, named or their loss even noticed.
Richard Grossman practices gynecology in Durango. Reach him at email@example.com. © Richard Grossman MD, 2012