This is the first recorded sighting of an otter on the islands.

David Steel, National Trust head warden on the Farnes, said: "It is staggering that an otter could survive the perilous journey out to the Farne Islands, especially Brownsman, which is along way from the mainland.

"We almost had to rub our eyes with disbelief when we discovered the tracks. We've recently had force nine gales and it can be tricky to reach the islands even on a relatively calm day, which makes this otters journey a little bit special."

The otter tracks, which stretch for 60 metres, were discovered in a muddy path on Brownsman, which had until recently been a boardwalk for visitors to the island.

Wardens are yet to see the otter but the agitated behaviour of the gulls suggests that it is still living on Brownsman and the outer group of islands.

In England and Wales otters are normally found living on rivers and they can be found on coastal sites in Scotland.

Northumberland has a healthy population of otters living on the major rivers and tributaries and this new addition to the Farne Islands will have made its way from one of these.

David said: "This is the first time that an otter has been recorded on the Farne Islands. We have no idea how long it might stay but the rocky islands offer it a safe place to live and it should be able to find an abundance of food."

Paul Chanin of The Mammal Society, who has written two books on otters and studied their recovery in England, added: "This is a really exciting discovery. We know that otter like living on the coasts where there is food available and will sometimes travel to islands but to find them so far off shore shows that they have a remarkable ability as navigators."