LONESOME GEORGE鈥橲 death in the Galapagos Islands may have signalled the end of the Pinta Island tortoises, but a related subspecies on a neighbouring island has been saved from extinction. The huge success of the rescue mission suggests that similarly endangered species may have a chance, too.
The Galapagos boast the world鈥檚 largest and tortoises. Throughout history, pirates and whalers have fed on the animals, and introduced pest species like goats to the islands, destroying the tortoises鈥� habitat. 鈥淕oats are very problematic,鈥� says at the University of Geneva, Switzerland. 鈥淭hey eat everything.鈥� As a result, the giant-tortoise population of Espa帽ola Island dwindled to near extinction four decades ago. In a bid to rescue it, conservationists in 1971 began collecting all the tortoises they could find on Espa帽ola 鈥� just 14 鈥� and took them to nearby Santa Cruz island to breed in captivity. They were joined by a 15th tortoise from in California.
In total, this breeding colony comprised 12 females and 3 males. Meanwhile, conservationists cleared Espa帽ola of goats. Baby tortoises were hand-reared until they were about 5 years old before being taken to Espa帽ola in batches. The programme was widely regarded as a success story. Since its inception, over 1700 tortoises have been reintroduced.
Advertisement
A true measure of success, though, is how well the animals are coping on the island 鈥� whether they are able to survive and breed when left to their own devices. All the new tortoises were born from the same 15 animals, so genetic diversity is thought to be low. That can cause a problem, as inbred animals die younger, have poor fertility, and are often more vulnerable to environmental changes. 鈥淭here鈥檚 always a big risk that the animals don鈥檛 survive or don鈥檛 breed,鈥� says Milinkovitch.
To investigate how well the tortoises were doing, Milinkovitch and his colleagues carried out a genetic analysis of all tortoises on Espa帽ola, searching for tortoises born on the island.
Eighteen years ago, none of the tortoises on Espa帽ola had been born there. From blood samples collected in 2007, the researchers have now found that about a quarter of the tortoises are native, the offspring of reintroduced animals ().
鈥淲e鈥檙e really excited,鈥� says Milinkovitch. 鈥淭he habitat is restored, the species is thriving and the animals are breeding happily. We can now safely say that the species is saved.鈥�
聯The habitat is restored, the species is thriving and the tortoises are breeding happily聰
鈥淚t certainly looks like it,鈥� agrees , UK, though researchers will have to check back in a couple of generations鈥� time to be sure.
Jean-Christophe Vi茅, deputy director of the , is more cautious: 鈥淚鈥檓 not sure you can ever say a species is completely safe.鈥� He gives the example of white and black rhinos in Africa, . But, since the start of this year, around 500 are thought to have been poached. 鈥淚t鈥檚 fragile,鈥� he says. But Vi茅 adds that the early success of the tortoise programme is encouraging. 鈥淲e need these kinds of successes. What is really important here is that you can do something about this extinction crisis. There is always hope.鈥�
