Image: Canna Island
Harvey Wood  /  National Trust for Scotland
Canna Island off the Scottish coast is home to about 15,000 seabirds and, finally, zero rats.
updated 6/8/2008 12:55:53 AM ET 2008-06-08T04:55:53

A tiny Scottish isle has successfully eradicated 10,000 rats after a three-year campaign to protect the island's seabirds.

Canna island's soaring cliffs are ideal nesting grounds and host about 15,000 seabirds from 14 different species, according to the National Trust for Scotland, which manages Canna.

But the birds found themselves under threat when brown rats, accidentally introduced to the island hundreds of years ago, began appearing in greater and greater numbers, something the trust said was probably due to warmer winters.

The rats were devouring the birds' eggs, killing their chicks and devastating many of their colonies. Some birds, like the long-winged Manx shearwater, were almost driven from the island entirely.

In 2005, the trust brought in a team of pest-eradication experts from New Zealand. Working with volunteers, they laid 4,388 traps out in a carefully plotted grid across the five-mile-long island, rappelling down the sides of cliffs to reach the more inaccessible areas.

Some 25 tons of rodenticide were shipped in to arm the traps, and by early 2006 the island's estimated 10,000-strong rat population had largely disappeared.

Authorities and volunteers have since been monitoring the island by leaving chocolate-flavored wax around Canna and keeping an eye out for the rats' distinctive nibble marks. With no confirmed rat sightings in more than two years, the British Environment Minister Mike Russell declared the island "officially rat-free."

Canna, more than 25 miles off Scotland's western coast, is home to about a dozen people.

"Rats, while being fairly innocuous creatures in their natural environment, can have a devastating impact in a fragile ecosystem such as that of Canna," Environment Minister Mike Russell said in a statement. "I am delighted to see the island declared officially rat-free and look forward to seeing its seabird population flourish."

"Canna is such an important habitat for seabirds in Scotland that we simply had to act to protect this important site and give our seabirds every chance to thrive," added Richard Luxmoore, an adviser with the National Trust. "Seabirds face so many threats from nature and man and need our help and protection."

"The seabirds are being monitored over this summer to see just what impact our efforts have had, but already things are looking good," he said. "We have already had the first recorded breeding of Manx shearwaters for over ten years."

The eradication program included steps to preserve a population of native field mice by moving them to the Edinburgh Zoo during the poisoning. "Their studies have shown that the mouse population has returned to thriving condition since the project," the National Trust said.

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