RARE pine martens could be strengthening their presence in Northumberland, according to survey results.

The elusive mammal, once through to be extinct in England, are cat-sized members of the weasel family which eat small rodents, birds and beetles.

They were first detected in Kielder Forest around five years ago on a wildlife camera and since then, sightings have increased.

Forestry England, who conducted the survey, began a new project last February to erect 50 denning boxes in part of the forest, which are used to provide artificial breeding sites for pine martens in areas where there is an absence of natural tree cavities.

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Another study site was established 15 miles away, but with no boxes present.

Experts want to compare activity at both locations to confirm providing the right number and design of den boxes in conifer forests improves the habitat for this recovering species.

Wayne Penrose, Forestry England ecologist, said four boxes showed clear evidence that martens used them for denning, while nearly four times the number of marten scats that were identified the previous year were discovered.

Persecution and habitat loss saw the pine martens' population crash during the 19th and early 20th centuries, with today's major stronghold in the Scottish Highlands.