Published online 27 January 2009 | Nature | doi:10.1038/news.2009.61


Goodbye Galapagos goats

Conservationists complete the largest-ever eradication of an island-invasive mammal.

GoatSantiago island is now goat-free.image100 / Alamy

Like many remote islands, the Galapagos Islands that fired Charles Darwin's imagination are both a hotbed of biodiversity and extremely vulnerable to invasive species.

Now a team of conservationists and scientists is reporting the largest eradication of a mammal species from an island ever achieved. All 80,000 or so goats (Capra hircus) on the 58,500-hectare Santiago Island have been eradicated in just 52 months.

Goats were successfully introduced to Santiago Island, which sits in the middle of the Galapagos archipelago, over the 1920s and 1940s. The goats grazed the island mercilessly, causing erosion, threatening the survival of rare plants and trees and competing with native fauna, such as giant tortoises.

After having eradicated pigs from the island, Filipe Cruz from the Galapagos National Park Service in Ecuador and his colleagues turned their attention to goats. From 2001 to 2005, the researchers hired large teams of local residents to cull the goats.

The goats were first herded into corrals by people on horseback wielding air horns and firing rifles. The captured goats were then killed humanely. Other goats were hunted on foot, with the help of dogs or by a large group hunting together in a line, combing the island.

Stubborn population

But the goats proved difficult to eradicate. In 2004, the teams used helicopters to help them spot and kill the animals. And finally, between 2004 and 2005, the teams used 'Judas' goats and 'Mata Hari' goats. The Judas goats were goats that had been captured from nearby islands and then released with radio collars to lead hunters to the last few goats. 'Mata Hari' goats — sterilized female Judas goats in chemically induced oestrous — helped to lure out otherwise wary male goats. An account of the eradication is published in the Journal of Wildlife Management1.

The island has been monitored since 2005 and now seems to be goat free. The eradication effort cost a total of US$6.1 million dollars, but more than one-third of that was spent on eradicating the last 1,000 goats and monitoring to make sure the job was done.

"It is very easy and cost-effective to remove the first 90% of the goats; it is very hard and expensive to get the last 10%," says Josh Donlan of Cornell University in Ithaca, New York, and an author of the paper. But, he adds that in the case of islands, "In the long run, eradication is going to be cheaper. It also makes sense from an ethical perspective, because in the end you are actually killing fewer animals."

The same group has since cleared the neighbouring Isabela Island of goats, Donlan says, which at a whopping 459,000 hectares is even larger than Santiago Island. However, that project has yet to be written up for publication.

Bounce back

As the goats disappeared, the plant life on Santiago bounced back, including some invasive plants such as blackberry (Rubus niveus). Control efforts are under way to weed them out. Meanwhile, native plants are also flourishing, and birds, such as the Galapagos rail (Laterallus spilonotus) have returned as well.

The project is among the most spectacular of a new wave of very ambitious island eradications. "It is incredibly inspiring," says ecologist Daniel Simberloff of the University of Tennessee in Knoxville, who blames "pessimism" for a lack of earlier attempts on this scale. "You have to decide in advance that you are going to stick it out and not get discouraged if the last ones are hard to get," Simberloff says. "I think there will be a lot more of this." 

  • References

    1. Cruz, F., Carrion, V., Campbell, K. J., Lavoie, C. & Donlan, C. J. J. Wildl. Manage. 73, 191–200 (2009). | Article |


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  • #60736

    I think that goat must've been having some serious PTSD.

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