NewScientist on Invasives Control on South Georgia

excerpt from the New Scientist at

Extermination in paradise

AS ISLANDS go, you would be hard pressed to find one more remote. Deep in the southern Atlantic Ocean sits South Georgia, a haven for wildlife in the midst of ferocious seas. Over 30 million birds of 31 species breed here and a further 50 species have been spotted. It is home to grey-headed albatrosses, northern giant petrels, white chinned petrels, Antarctic prions, half of the entire population of macaroni penguins and most of the planet’s population of the South Georgia blue-eyed shag.

But it is not as idyllic as it sounds. Under the surface lurks a menace that is slowly ripping the ecosystem apart: rats.

The rodents were stowaways on sealing and whaling ships that visited the island until the mid-20th century. When the hunters stopped coming, the rats were left to their own devices along with a small population of reindeer that had been brought for food and now roam wild. Without natural predators, the rat population has swollen to many million, eating their way through tens of millions of ground-nesting birds’ eggs and chicks in the process. As a result, the island’s endemic wildlife is under threat, and its only songbird, the South Georgia pipit, is on the brink of extinction.

Now the South Georgia Heritage Trust (SGHT) is going to fight back. In what will be the largest mass extermination ever attempted, the SGHT plans to poison every rat on the island. “The difference between success and failure is the survival of two rats on the entire island,” says Tony Martin, project manager of the SGHT Habitat Restoration Programme. “We don’t have to get rid of most or even 99.9 per cent of the rats – we have to eradicate 100 per cent.”

Absolute eradication is the only option because rats breed rapidly. They can live for around two years, achieve sexual maturity at two months old and are able to produce seven litters of 8 to 10 offspring a year. Female rats reach menopause at around 18 months. Even in the harsh climate of South Georgia, a sexually mature female is likely to have around four litters a year. If just one couple survive, it will only take a few years before the island is overrun again (see diagram).

go to the link above for graphics and the rest of the article . . . 

Sanjida O’Connell is an editor in New Scientist‘s Opinion section

About Bruce

Work for sustainable development of small islands and the Chesapeake Bay; ex-Peace Corps (Volunteer and staff) in LA & Caribbean; cruised Caribbean on S/Y Meander for three years; like small tropical islands, French canals, Umbria, Tasmania, and NZ. Married 52 years to the late Kincey Burdett Potter (see President of the now-sunsetting Island Resources Foundation.
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