LONESOME GEORGEāS 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 worldās largest and tortoises. Throughout history, pirates and whalers have fed on the animals, and introduced pest species like goats to the islands, destroying the tortoisesā habitat. āGoats are very problematic,ā says at the University of Geneva, Switzerland. āThey eat everything.ā As a result, the giant-tortoise population of EspaƱola 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 EspaƱola ā just 14 ā 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 EspaƱola of goats. Baby tortoises were hand-reared until they were about 5 years old before being taken to EspaƱola 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 ā 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. āThereās always a big risk that the animals donāt survive or donāt breed,ā says Milinkovitch.
To investigate how well the tortoises were doing, Milinkovitch and his colleagues carried out a genetic analysis of all tortoises on EspaƱola, searching for tortoises born on the island.
Eighteen years ago, none of the tortoises on EspaƱola 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 ().
āWeāre really excited,ā says Milinkovitch. āThe habitat is restored, the species is thriving and the animals are breeding happily. We can now safely say that the species is saved.ā
ĀThe habitat is restored, the species is thriving and the tortoises are breeding happilyĀ
āIt certainly looks like it,ā agrees , UK, though researchers will have to check back in a couple of generationsā time to be sure.
Jean-Christophe ViĆ©, deputy director of the , is more cautious: āIām not sure you can ever say a species is completely safe.ā 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. āItās fragile,ā he says. But ViĆ© adds that the early success of the tortoise programme is encouraging. āWe need these kinds of successes. What is really important here is that you can do something about this extinction crisis. There is always hope.ā
