Rat eradication: islands fighting back against killer rodents


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Uplifting news from Lundy (Devon) reveals that, since a rat eradication programme began on the island ten years ago, the island's Manx Shearwater population has been subject to a massive increase, with RSPB survey teams returning to the island this spring to find that the population had grown tenfold in that time from 300 to 3,000 pairs. Helen Booker, RSPB Senior Conservation Officer in the Southwest, said: "This is such an exciting result, better than we expected, and the rate of increase is an indication of just how important rat-free islands like Lundy are as breeding site for seabirds."

It is not just the shearwaters, though: Puffin numbers have also increased from 5 to 80 birds and Guillemots, Razorbills and Shags have also seen substantial increases. Anecdotally, other species such as Pygmy Shrew and Wheatear are also more numerous.

Derek Green, Lundy General Manager, said: "We are delighted with this result, which is showing benefits for a range of species on the island and shows just how much can be achieved. Lundy has been a wildlife haven for many years, although rats were always a problem we had to live with. Their removal has transformed the island for both wildlife and visitors alike, and we're watching with great anticipation and excitement as the cliffs and slopes of Lundy fill with the eerie calls of thousands of birds once again."

Dr. David J. Bullock, Head of Nature Conservation for the National Trust, said: "Once the rats had gone from Lundy, the number of pairs of shearwaters on Lundy went from hundreds to thousands in matter of a few years, which is outstanding news. Such a rapid recovery is unlikely to have been due to "home-bred" birds. Shearwaters from other colonies must have settled to breed on the island. We do not know where these birds came from, but there is a massive shearwater colony on the islands off Pembrokeshire in Wales. So was Lundy repopulated in part by the Welsh?"

Manx Shearwater
Manx Shearwater, Northern Rocks, Isles of Scilly (Photo: Joe Pender)

The striking results from Lundy are an indication of what can be expected a couple of hundred miles to the southwest as the Isles of Scilly Seabird Recovery Project gets underway this summer. This ambitious project seeks also to secure a legacy for similar seabirds and the Scilly Shrew, as well as the community that lives and works not just on the islands of St. Agnes and Gugh, but across the archipelago.

The Isles of Scilly Seabird Recovery Project is now the largest community-based island restoration project of its kind in the world, and will provide a raft of benefits in the islands for the 25 years of the project's life, and beyond. It is managed by a coalition of groups including RSPB, Isles of Scilly Wildlife Trust, Natural England, Duchy of Cornwall, the Isles of Scilly Area of Outstanding Natural Beauty (AONB) partnership and a representative from the islands of St. Agnes and Gugh, with support from the Isles of Scilly Bird Group.

Jaclyn Pearson, Project Manager for the Isles of Scilly Seabird Recovery Project, explained: "Lundy has pioneered this type of project in the UK and it demonstrates just what devastating effects the rats were having on the island's wildlife. Lundy is now the most important place in England for Manx Shearwater, leaving the Isles of Scilly in its wake. This really has thrown down the gauntlet and in years to come it will be very exciting seeing the changes here."

David Appleton of Natural England, who has been involved in both these projects, said: "Following Lundy's example, in the 25-year lifetime of the Isles of Scilly project we can only imagine what the population of Manx Shearwater and European Storm-petrel will be in the southwest of England."

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South Georgia

Since the rats arrived on South Georgia aboard sealing and whaling ships in the 19th century, they've been wreaking ecological havoc on the island and its ground-nesting seabirds by preying on the birds and their eggs. However, this is all set to change. Enter an international team of wildlife biologists, who have recently completed the second phase of history's largest rat eradication programme on the remote island.

Braving appalling weather in the run-up to the Antarctic winter, the group's helicopter pilots logged hundreds of hours in perilous flying conditions to spread nearly 200 tons of at poison over 224 square miles (580 square kilometres) of South Georgia's coastline. The ultimate goal: To rid this once supreme seabird habitat of its millions of rats once and for all. South Georgia was probably the richest seabird breeding area in the world when Captain James Cook visited in 1775. Now, the island has less than 1% of its original seabird population — this being attributed to rats.

This recent bait drop follows a successful trial two years ago, which cleared 10% of South Georgia of the invasive rodents. Next year, Tony Martin of the University of Dundee said, the group plans to return and finish the job, hopefully rendering South Georgia rat-free by 2015. "This is ten times bigger than anything that has ever been attempted anywhere else," Martin said.

Wandering Albatross
Wandering Albatross, South Georgia (Photo: Steve Copsey)

South Georgia's ambitious rat eradication campaign may be the world's biggest at the moment, but it's far from the only one. Many of the world's most biologically important island ecosystems have been invaded by rats. And, while islands may represent only 5% of the world's land mass, they account for half of the world's endangered species. As such, eradicating rats is crucially important to preserving many of these species.

As of last count 435 islands around the world have been cleared of rats, according to Island Conservation, an organization that works to remove invasive species on islands. It's a number that is growing quickly, and so is the success rate.

The projects try their best not to hurt the species they're supposed to protect. For one, the rat poison, brodifacoum, is not water-soluble, so it can't leach into the groundwater or poison waterways. Some seabird scavengers could eat stricken rats and become ill, though the rat carcasses are hard to find: The poison makes the rats photophobic, or shy of light, so the rodents usually retreat to their burrows before dying. It's possible that a few duck or other birds may ingest the poisonous pellets, but since rats eat thousands and possibly millions of chicks a year overall, poison is still the better strategy, experts say. Each island brings its own challenges — for example, South Georgia receives some ferocious weather and there are also lots of large birds sharing the airspace with the helicopters employed to drop the poison.

New Zealand

New Zealanders lead the field when it comes to getting rid of rats, according to Martin. "They began focusing on rat eradication on their own islands back in the 1980s in order to try to preserve their native wildlife. Over the years they've had a lot of successes, developed a huge amount of expertise, and in the 1990s began perfecting the science of using helicopters to make aerial bait drops over large areas."

New Zealand's successful campaign to remove nearly a quarter of a million Brown Rats from Campbell Island — a 44-square-mile (114 square kilometre) sub-Antarctic island — was the world's largest rat eradication project when it was completed in 2001. Twelve years later the island is rat-free and the once critically endangered Campbell Island Teal has bounced back.

Sophisticated poison dispersal techniques using GPS guidance and specially designed spreader buckets slung under the helicopters were developed for the Campbell Island operation, and went on to pave the way for the much larger one on South Georgia.

Lord Howe Island, Australia

A US $9 million programme to eradicate an estimated 130,000 rats on the island, a subtropical paradise located 370 miles off Australia's eastern coast, was launched in July 2012. Rats originally arrived aboard the SS Makambo, which ran aground on the north end of the island in June 1918. It was a catastrophe — at least 30 species of wildlife have since disappeared completely from the island, while another 13 species remain under threat. Lord Howe Island has often been cited as a worst-case example of rat devastation.

Queen Charlotte Islands, British Columbia

Sometimes described as the Galápagos of the north, the chain of islands in British Columbia has some of the largest remaining seabird colonies in Canada. At one time these seabirds could be counted in the hundreds of thousands, but three centuries of rat infestation have whittled their numbers down to 20,000 or so. Last September, a rat eradication programme was launched, and so far two of the islands have been cleared of rats.

Galápagos Islands, Ecuador

The breath-taking island chain off Ecuador's coast, famous for its bird and reptile life, is home to an estimated 180 million rats — courtesy of the whalers who often stopped here in centuries past. As elsewhere, the rodents have been an ecological disaster, devouring every single tortoise hatchling for the past hundred years. Last November the Ecuadorian government set into motion South America's biggest rat eradication scheme, hoping to have the island chain free of rats by 2020.

Waved Albatross
Waved Albatross, Galápagos Islands (Photo: Mick Dryden)

Original article on rat eradication on islands adapted from the National Geographic website.

Written by: RSPB/National Geographic