Camera footage of the animal, installed as part of a red squirrel monitoring project, was first seen by John Hartshorne, who manages the fieldwork and ecology education organisation Albion Outdoors.
John said: “Historically, pine martens were commonplace but habitat clearance and persecution has led to them being eliminated from nearly all of England.”
Mike Pratt, chief executive of Northumberland Wildlife Trust, added: “As a natural predator they have the potential to help manage the grey squirrels and they are a part of our woodland and forestry ecosystem so we need them here.
“Their presence is also great from a nature tourism perspective.
“We look forward to working with Forestry Commission England and the Vincent Wildlife Trust to help them establish a colony over time.”
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