Field Notes: Pine martens on camera at Thirlmere

Thirlmere Resilience Project Officer Isaac reveals what the cameras recorded when pine martens appeared at Thirlmere, a year after their reintroduction to Cumbria in late 2024

A group of pine martens were released in South Cumbria back in late 2024 as part of a reintroduction project and have been spreading rapidly ever since. In January of 2025, we spotted our first marten at Thirlmere, Philomena, who was one of around 14 individuals released under licence.

Camera traps set up across the county have revealed that the martens are travelling huge distances from their release site.

Back in September, a young female took up residency in the Oak woodland site on the western side of the reservoir back. The team named her Birch, and we have been seeing her regularly on our camera trap, having recently placed a den box for her in a nearby tree.

Just before Christmas, we were thrilled to see footage of a new marten at Thirlmere. A large male has moved in very close to where Birch is currently living. After the Christmas break, I checked all our cameras and found footage of Birch and this male playing together on Christmas morning.

Pine martens breed in summer and delay their pregnancy until the following spring, so we hope to see these two stay together long enough to mate and produce kits in 2027.

• Watch the full camera trap video of Birch here