Fears have been voiced that the trawler which ran aground on St Kilda on Friday could threaten rare sea birds on the World Heritage Site.
The Spanish trawler ran aground in the early hours of Friday
Force 11 gales have dispersed fuel from the vessel's tanks but the National Trust for Scotland fears it is any rats on board that could cause most damage.
The trust, which has owned the islands since 1957, said it would be a "huge problem" if rats got ashore.
It said rat colonisation would destroy the archipelago's sea bird population.
The trust said St Kilda, which is currently completely rat-free, is home to one of the biggest populations of gannets in the world, one of the biggest colonies of puffins in the UK and about 90% of Europe's Leach's storm petrels.
All of those birds nest on the ground or in burrows and the trust said that if one pregnant female rat got onto the archipelago her offspring would soon decimate next season's eggs and chicks.
The conservation charity has implemented anti-rat contingency plans, which involve laying traps at the points that are most at risk.
The trust said rats would devastate sea bird colonies
It has focused on the environmental implications for Hirta, the largest of the four islands.
Susan Bain, who looks after the island on behalf of the trust, said: "St Kilda's remote isolation means that there are no land-based predators on the bird colonies and we've got strict guidelines to make sure people don't accidentally bring non-native species such as cats or rats onto the islands.
"We have to act on the assumption that there are rats on the trawler.
"And it would only take one pregnant female from the ship to get ashore to devastate the bird populations."
During the winter, the only people based on St Kilda are staff at the Ministry of Defence radar station.
The trust has asked them to put down traps, ahead of the arrival of specialist staff on Tuesday, who will erect monitoring stations with chocolate flavoured bait and chew sticks.
They will be able to tell by the tooth marks if it has been chewed by mice, which do live on the islands, or by rats.
"Rats on St Kilda would really matter, because the islands are one of the most important sea bird stations in the north east Atlantic," Ms Bain said.
"Rats would go through those colonies, eating eggs and chicks. And if that happened it would be after four poor breeding seasons.
"These birds are already heading into a crisis. They really don't need another stress."