It is the first time otter tracks have been found in the Farne Islands
An otter has survived a "perilous" three-mile sea crossing to the Farne Islands for the first time, the National Trust has said.
The animal, more commonly found in rivers, has swum from the coast of Northumberland despite rough seas.
Head warden David Steel said he was stunned to find 60 yards of otter tracks on Brownsman Island, which is famed for its bird colonies.
The mammal has not yet been sighted, but it is thought to be still there.
Agitated behaviour by the island's gulls and puffins suggest the new predator has settled in.
Force nine gales
While otters in Scotland do live in coastal areas, Mr Steel said it was "a rare event" to see them by the sea in England.
For one to reach an island three miles offshore was, he said, "incredible".
"It is staggering that an otter could survive the perilous journey out to the Farne Islands, especially Brownsman, which is a long way from the mainland," he said.
"We almost had to rub our eyes with disbelief when we discovered the tracks," he told the BBC.
"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 otter's journey a little bit special."
Mr Steel said the otter may be a young animal, fresh from leaving the family fold and seeking its own territory.
"It might be a lonely animal, but it will hopefully survive," he said.
"There'll certainly be plenty of food, plenty of crustaceans and fish to feed upon, but unfortunately, unless another animal swims out here, it might have a lonely existence.
Otters numbers suffered a huge decline in the 1950s and 1960s
"But there's no reason why we can't get a second or third animal. They are obviously exploring this area so, who knows, maybe in the future might have a small breeding population."
The only worry, Mr Steel said, was about the impact the otter might have on nesting birds next summer.
"Unfortunately, otters are carnivores. They will feast upon bird eggs and small chicks so at that moment it may be a slight concern."
In the late 1950s and early 60s, otters underwent a sudden and catastrophic decline throughout much of Britain and Europe, probably due to the combined effects of pollution and habitat destruction.
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