Scottish forests protective forts for red squirrels

Twenty natural strongholds would protect red squirrels in Scotland even if grey squirrels were to run rampant across the country, a new study shows.

The UK's red squirrels are under threat from their invasive, north American grey counterparts. Scotland is now home to around 75% of all the UK's red squirrels.

A variety of conservation measures have been implemented or proposed, from grey squirrel culls to creating managed strongholds.

A new study from Heriot-Watt University and Forestry and Land Scotland (FLS) shows that over 20 forests in Scotland could act as natural strongholds for red squirrels.

Professor Andy White, a mathematical biologist at Heriot-Watt University, developed a computational model to determine whether the current composition of Scotland's forests could protect red squirrels.

Professor White said that their "model shows that, even in a worst case scenario, if greys are allowed to run rampant around Scotland, red squirrels will find haven in these natural strongholds."

"This is great news for red squirrels. About 10 years ago, it was a real worry that grey squirrels would spread north through Scotland and wipe out the reds. Red squirrels dominate in coniferous forests, whereas grey squirrels do better in broadleaf and mixed forests. The current policy is to create 19 managed strongholds for the reds, where broadleaf trees are removed and replanted with conifers that would protect their red populations. However, this would reduce tree species diversity for other species. Our model shows that over 20 existing forests in Scotland would act as natural strongholds for the reds. This means we don't have to remove broadleaf species like oak. Natural strongholds could conserve red squirrel populations while simultaneously maintaining forest diversity."

White and his team combined satellite data with tree species' locations and field data that linked red and grey squirrel populations to different tree types. They then built a model that represented how red and grey squirrels compete for resources in different forests.

They found natural strongholds from Eskdalemuir forest in Dumfries and Galloway in the south to Newtyle forest in Moray in the north of Scotland.

Kenny Kortland, FLS wildlife ecologist said that "this modeling work confirms that forest landscapes managed for timber production create safe havens for viable populations of red squirrels, even if grey squirrel populations were to expand."

"This is great news, as we can all continue to use timber products from Scotland safe in the knowledge that the sector supports one of Scotland's most popular species."

The research was published in Nature Conservation.