By John R. Platt
Now here’s a great conservation success story: After more than 100 years, Galápagos giant tortoise hatchlings finally have a chance to thrive and survive on their native Pinzón Island, after conservationists cleared it of the invasive rats that nearly wiped out the animals.
Like most Galápagos giant tortoises—including the conservation icon Lonesome George, who died last year—the tortuga subspecies that once lived on Pinzón Island was nearly wiped out by the arrival of pirates, fishermen and invasive species in the seventeenth and eighteenth centuries. In this case, the greatest threat to the Pinzón Island tortoise subspecies (Chelonoidis nigra duncanensis) came in the form of voracious black rats (Rattus rattus) and Norway rats (R. norvegicus), which ate both the tortoises’ eggs and their defenseless hatchlings. Older tortoises can defend themselves against rats but so many young animals were killed by rodents that the subspecies could not replenish its population as older animals died off. By the beginning of the twentieth century, it appeared that no young tortoises on the island were surviving until adulthood.
Conservationists took the first step toward saving the Pinzón Island tortoises in 1965 by collecting as many of the animals as they could and placing them into captive breeding programs. Tortoises were then hatched and reared on other islands and brought back to Pinzón Island once they were old enough, but the impossibility of successful breeding on their home island led to the subspecies being classified as extinct in the wild.
The next step began a few years ago when Galápagos National Park and its partners launched a program to eradicate the rats and other invasive species throughout the archipelago, starting on smaller islands such as Pinzón, which as of last year was home to an astonishing 180 million rats. Last December more than 20,000 kilograms of poison were dropped on the 18-square-kilometer island. The poisons, which dissolve after a few days, were specially designed to attract rats but repel birds and other wildlife that might accidentally consume them. The rodents quickly took the bait and Pinzón has now been tentatively declared rat-free. More....