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The world's most extensive island rat eradication is complete, with the crowning achievement in the form of a bucket of Bell manufactured bait dropped via helicopter onto the sub-Antarctic South Georgia Island.

 

The final, Phase 3 of the project started in January 2015, as a ship loaded with three helicopters and almost 100 tons of specially manufactured Bell bait left from the Falkland Islands off the coast of Argentina.

The unrelenting winds and erratic weather patterns proved challenging, but not overpowering. One helicopter even sustained severe damage due to rough weather, threatening to halt the final Phase completely.

Despite varying weather conditions and the arduous task at hand, the project reached its culmination at the end of March, when the last of the pellets dropped onto the island below.

The project, led by the South Georgia Heritage Trust (SGHT), was a five-year, $11 million project. It began with the goal of total eradication of invasive rodents that were threatening the native wildlife at the seabird sanctuary.

Dropping bait in flight

"After many years of preparation, three seasons of fieldwork, more than 800 bait loads, a thousand helicopter flying hours and over a thousand square kilometers treated, the final pellet had been dropped," said Professor Tony Martin, Project Leader from the University of Dundee, in his recent recount in a South Georgia Heritage Trust newsletter.

The island is one of the world's most important breeding sites for unique bird species. Migratory birds like blue petrels, the pipit and the South Georgia Pintail, along with large seabirds such as albatrosses and penguins all inhabit the island.

In the two previous phases in 2011 and 2013, the team, nicknamed Team Rat, successfully baited and eradicated rats from the first two-thirds of the island. Even at the point, the project was five times larger than any other rodent eradication project yet attempted.

During Phase Three, the team of 18 aerially spread Brodifacoum Conservation Pellets on the remaining one third of the island, an area of about 140 sq. miles. The operation involved almost 450 flying hours and utilized GPS, data management, meteorology and polar logistics to get the job done as efficiently as possible.

Pintail chicks

History of South Georgia Island

South Georgia Island is located in the Antarctic about 1,000 miles off the southern tip of South America and is rightly celebrated for its wildlife. The remote island is a breeding ground to over 29 bird species, and over 30 million birds nest and bring up young chicks on the island every year.

While the island's rich biodiversity and prime location for migratory sea birds supports a diverse wildlife population, it also attracted the sealing and whaling industries in the early 1900's. These lucrative industries practically wiped out the islands' seal and whale populations before the practice was later banned.

While the industries are long gone and the marine life has since bounced back, the legacy of the Norway rat remains. The rats, introduced by sailors, have since devastated South Georgia's seabird populations, causing a drop by more than 90%.

South Georgia's sea and land species - petrels, the pipit, and prions - are particularly susceptible to Norway rats that prey on the eggs and chicks of nesting seabirds. The lack of trees on the island means birds must nest on or under the ground, right within reach of the predatory rats.

Due to the remote location, and the vast square footage of the island, many scientists feared any rat eradication project would be too challenging of a mission to tackle.

Because rodents easily fill any available niche, an island normally must be treated with bait all at once. South Georgia was an exception.

The island held numerous glaciers that were nearly a mile across, too far for the rodents to travel. Each glacier extended into the ocean, creating effective barriers to reinfestation of previously treated areas.

Warming seas and an accelerating melting of the glaciers nearly spoiled this advantage but SGHT and Team Rat were able to complete the entire project in time.

Another unique challenge in a location as remote and harsh as South Georgia was the weather. Temperatures could vary from a warm 50 degrees one day to an unrelenting blizzard the next.

Despite the daunting task, the hope for a rat-free South Georgia Island became a rallying cry for Team Rat - vowing to reclaim the Island for the seabirds.

Behind Bell's Island Bait

In order to reduce the exposure to non-target species, SGHT performed extensive studies beforehand to learn about the biology and species living on or visiting the island. The shape, color and size of the pellets were carefully considered and tested to minimize non-target primary and secondary poisoning, while remaining palatable for rodents.

For South Georgia Island, this meant a large, green pellet that was sturdy and large enough to survive aerial baiting. Too large for most of the bird species to easily consume, but small enough for rodents to eat. Lumitrack was also incorporated to aid in tracing the bait distribution and ingestion.

Team Rat was able to take advantage of the fact that most of the indigenous birds on South Georgia are seabirds that eat marine prey, so the Brodifacoum Conservation Pellets were not a tempting meal.

The project was also intentionally conducted at a time when migratory bird presence on the island was expected to be at a minimum.

Hope for FuturePipit

While all three phases of bait application are now complete, there is still extensive work to be done. Two additional years of follow-up monitoring are required before South Georgia can officially be deemed "rat-free".

The team will closely monitor the island for any sign of rodents by checking rodent chew sticks placed throughout the island following each of the baiting phases.

The first bird likely to recover is the resident South Georgia pipit. "If pipit song is heard, and certainly if young pipits are seen, we can be sure that the rats have gone," said Tony Martin.

The completion of Phase Three is a momentous event for SGHT, Team Rat, and Bell Labs. With half of the world's endangered species living on islands, the need to stop damage done by invasive rodents and restore the ecological balance to these islands is a demanding but necessary responsibility.