Pine marten monitoring could help red squirrel conservation

Once found across Britain, the pine marten was prone to persecution until relatively recently. Though it has recovered a little from a dramatic decline, the species is still rare. Scotland’s population is estimated at 3,700 adults.

It is a cat-sized member of the weasel family with dark brown fur, save for a large, creamy white patch on its throat.

Pine martens prefer native woodlands but can also live in conifer plantations and on rocky hillsides.

A new technique that uses thermal imaging cameras to capture the occupancy of over 100 artificial den boxes in Galloway Forest detected a number of baby pine martens (called kits).

A pine marten (Image: Forestry and Land Scotland)

Trail cameras were subsequently fitted to 14 den boxes which provided a positive heat source (indicating evidence of occupation) in order to capture subsequent pine marten movements.

Footage captured on the cameras – fitted by the Dumfries & Galloway Pine Marten Group – shows the kits being moved at around four weeks old by the mother, one at a time, down to a denning site closer to ground level so they’re less likely to injure themselves when they become more mobile.

The FLS thermal imaging trials have been taking place over the last 12 months.

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The handheld thermal imaging cameras can detect a heat source in the pine marten den boxes all year round, especially during crucial periods such as in spring when pine marten kits are born and also in winter when den boxes are used for shelter in harsh weather.

Speaking about the trials, Kim Kirkbride, Environment Forester at Forestry and Land Scotland, said, “Using the non-invasive thermal imaging camera allows us to remotely monitor how many den boxes are in use, without disturbing the inhabitants.

“We can establish whether populations of pine marten are increasing and if they’re breeding successfully. Pine martens are an important factor in grey squirrel control.

A pine marten (Image: Forestry and Land Scotland)

“We still have to carry out grey squirrel control, but the presence of the artificial dens in the national forest estate, helps to support pine marten numbers and importantly, the survival of the reds.”

Pine martens were once common in Scotland, but their population declined due to trapping and killing by local gamekeepers.

The animals are prized for their valuable fur, and can also lose habitats due to farming and other agricultural practices.

It's thought they could be useful in controlling the population of grey squirrels.

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Pine marten are known to naturally predate upon squirrels and prefer greys over red squirrels as greys appear to be slower moving and less wary and therefore easier to catch.

Galloway has a large population of red squirrels, which are vulnerable to the greys which both compete with them for food and carry squirrelpox.

The grey squirrel was introduced from North America and has natural immunity to the virus, something the native species does not have.

Red squirrels were once prevalent throughout the UK but the disease and competition have reduced their numbers to around 140,000.

Most of these are in Scotland, largely in the Highlands, Dumfries & Galloway and the Isle of Arran where the water creates a natural barrier to the invasive species.

Forestry and Land Scotland (FLS) erect artificial pine marten boxes in areas where red squirrel populations are particularly under threat because pine martens are slow breeders and artificial dens can help improve breeding success locally.

Plantation or productive forests - in particular soft wood grown for timber - do not offer an abundance of the safe, warm and dry tree cavities that the martens prefer to den in.

The artificial dens are installed around four or five metres off the ground.

They constitute wooden boxes with roofs to keep the rain and wind out and wood shavings inside them to encourage nesting.

Last year FLS announced the installation of artificial pine marten dens along the east coast of Scotland and in Perthshire to help ward off advancing grey squirrels in the region.

FLS hope to use this technology at other sites across Scotland to help monitor pine marten on both a local and national level.