Pest controllers from New Zealand claim to have wiped out the rat population on a small island near Skye.
Rats on Canna were blamed for eating birds' eggs
Rat catchers from Wildlife Management International killed 10,000 rodents threatening bird populations on Canna.
During a six month operation the team laid poison and rat traps on the orders of the National Trust for Scotland.
Elizabeth Bell, project manager, said: "If the monitoring over the next year discovers that even one rat is present, we will take action."
The rats first arrived on the island on ships about 100 years ago and had been feeding on seabirds' eggs.
As a result, they were blamed for a serious decline in the bird species which have inhabited Canna over the last 10 years.
Richard Luxmore, head of nature conservation at the National Trust for Scotland, said: "It is vitally important that we make sure there are no rats left on Canna if we are to regenerate the island's internationally important seabird colonies.
"We will be monitoring the seabird colonies closely this summer and hope to see an improvement in their populations now that the rats appear to have gone."