Rat's the way to do it – island seeks ranger to help keep vermin at bay

• The shipwreck of a Spanish fishing boat on St Kilda saw traps set to ensure no rats escaped on to the islands

But as the ranger's post on St Kilda is advertised for the 2010 season, a more quirky requirement of the contract has emerged. For the successful candidate for the 16,457-a-year post must have excellent rat-trapping skills.

There are currently no rats on the remote British outpost, 41 miles west of Benbecula in the Outer Hebrides, and the National Trust for Scotland (NTS), which owns the remote archipelago, intends to keep it that way.

NTS Western Isles Area Manager Susan Bain said keeping rats at bay was as important a part of the ranger's job as monitoring seabirds and welcoming the thousands of visitors who flock to St Kilda on cruise ships and leisure craft.

Laying rat traps every time the island supply boat docks is an essential part of the ranger's tasks. Ms Bain said: "We don't have any land-based predators at all. The ranger must see that we don't have any invasive species and the most obvious one is rats.

"There are rat traps put down when they are loading the supply boat at South Uist, there is a pest control officer on board and when the boat comes in to St Kilda to unload, the ranger will put out the rat traps there."

The supply boat, which, weather permitting, makes regular trips from South Uist to bring food and other essential supplies to St Kilda, is the only vessel allowed to berth there.

Other seafaring visitors must leave their boats away from the shoreline and transfer passengers to the village of Hirta in small dinghies – another step to keep rats at bay. When 10,000 rats invaded the isle of Canna in 2008, threatening bird nests, the NTS spent a fortune eradicating the rodents.

Ms Bain said: "It cost hundreds of thousands of pounds to get the rats off Canna; it was a specialist New Zealand team that was brought in. It's far better to be safe than sorry. We have to ensure that people don't bring their pet rat, or cat, or ferret, on to St Kilda. That is one of the main threats to St Kilda's World Heritage status. The main fear is that they would eat the birds' eggs and they might also go out to eat the St Kilda mouse."

She said keeping out invasive species was one of the main problems for special islands around the world, including the Galapagos Islands, where people unwittingly introduced goats. Ms Bain said: "The problem is that they have got all sorts of things that are literally eating their way through the local wildlife. It's a much bigger problem because they are there."

As the search for a new ranger gets under way Ms Bain said: "There are always a lot of applicants for the St Kilda ranger job. It's a sort of goal for a lot of people within that type of business, particularly people who are working in seabird colonies."

BACKGROUND

St Kilda is Europe's most important seabird colony.

The world's largest colony of gannets nests on Boreray in the St Kilda archipelago.

The UK's largest colony of fulmars is found on St Kilda.

The native population of St Kilda were evacuated in 1930.

St Kilda is the only place in the UK awarded mixed World Heritage Status for its natural and cultural significance.