Lonesome George, Not So Lonesome?

Published August 22, 2008

Last month brought news that 13 eggs where found in Lonesome George's pen. The last of the Galapagos' Pinta Island species of giant tortoise, scientists at the Charles Darwin Research Station have been attempting to breed George with tortoises similar to Pinta subspecies since 1972. Over thirty-years later (giant tortoises have never been celebrated for their swiftness) finally, there is hope that their efforts may have paid off.

On July 21, 2008, Park rangers found a nest in George's corral with nine eggs -- three of which were intact, two of which had tiny cracks, and four of which were broken entirely. Eight more eggs were found in a new nest this morning [Aug 22, 2008] -- all eight eggs were in good condition. The Park staff has taken all thirteen eggs and placed them in incubators at the Charles Darwin Research Station. Eight eggs are set at an incubation temperature of 29.5ºC and five are at 28ºC.

In certain species of reptiles (including Galapagos tortoises), there are no chromosomes which determine gender. Gender is determined by the temperature at which the eggs are incubated. The higher temperatures produce females and the lower temperatures produce males. After many years of experimentation during the 1980s at the Research Station, staff discovered the temperature range at which the eggs would produce males and females. In this particular case, given the number of possibly viable eggs, the decision was made to put more eggs at the higher incubation temperature (female). In a population restoration effort, which this certainly is, it is more important to have more females than males.

There are now a total of 13 eggs in the incubators -- 5 from the first tortoise and 8 laid by the second. It will be another 120-130 days before the incubation process is completed and before it is known if the eggs are viable.

Galapagos enthusiasts will remember that George, the last remaining Pinta Island tortoise, was brought to the Research Station in 1972 with the hopes that he might breed with tortoises similar to the Pinta subspecies. His two new companions were brought from Volcan Wolf (the northernmost volcano on Isabela Island) because morphologically they were the most similar to Pinta tortoises. We now know through genetic studies that tortoises from Espanola are genetically closest to the subspecies from Pinta. We also now know that a hybrid tortoise was discovered on Volcan Wolf (Isabela) which shares half of its genetic material with Geochelone nigra abingdoni.

With the two female companions in place in George's corral, scientists began to work on sexual stimulation, to try and induce George to reproduce. A Swiss volunteer, Sveva Grigioni, worked with him during a four-month period, but there were no advances. Animal nutritionists and veterinarians with expertise in tortoises were consulted. A diet rich in minerals and vitamins, prescribed by a nutritionist from the National Zoo in Washington, DC, helped to improve George's overall health. But nothing appeared to produce results.

Until, perhaps now. The Park staff is working directly with geneticists to determine if there is any sufficient material from the broken eggs to determine the genotype of the father (whom everyone certainly hopes is George!). At the same time, the Park is waiting patiently for the first signs of development within the incubated eggs. With both females now engaged in egg laying, we are optimistic that there will be additional good news soon from Puerto Ayora.

Reproduced with permission from the Galapagos Conservancy. August 22, 2008