• The red squirrel populations are in decline with estimates indicating the UK red squirrel population is now under 140,000 compared to 2.5 million greys.
  • A study by Heriot-Watt University and Forestry and Land Scotland (FLS) looks at ways the red squirrel be pulled back from the brink of extinction.
  • Researchers have identified areas of forest in Scotland that offer an ideal habitat for red squirrels but lack the kinds of trees that grey squirrels need to thrive.

The red squirrel holds a special place in British culture, partly because it features as a playful character in a number of children’s books that have proved popular for generations.

So when the people of Scotland were asked in a poll to name their favourite wild animal, it’s perhaps no surprise that the red squirrel came second only to the majestic golden eagle.

Red squirrels are endangered in the UK. Their decline began in the 1870s when the larger grey squirrel was introduced from North America as a decorative feature in the gardens of the wealthy. The greys quickly escaped into the wild, outcompeting the red squirrels for food and habitat. The grey squirrel also carried the squirrelpox virus to the UK. The virus is harmless to grey squirrels but fatal to the reds.

Estimates indicate the UK red squirrel population is now under 140,000 compared to 2.5 million greys.

Forests to the rescue of red squirrels

So how can the red squirrel be pulled back from the brink of extinction in the UK?

A study by Heriot-Watt University and Forestry and Land Scotland (FLS) offers one possible solution. Researchers have identified areas of forest in Scotland that offer an ideal habitat for red squirrels but lack the kinds of trees that grey squirrels need to thrive.

Red squirrel distribution (in green).
Scotland's forests are one of the only remaining refuges for the red squirrel.
Image: ‘Britain’s Mammals 2018: The Mammal Society’s Guide to their Population and Conservation Status.’

Red squirrels do better in coniferous forests, while greys tend to thrive in broadleaf and mixed forests. One current conservation strategy involves removing broadleaf trees. This protects the red squirrel but harms the wider ecosystem.

That’s where Professor Andy White comes in. He’s a mathematical biologist at Heriot-Watt and he’s built a computer model to establish whether the existing composition of Scottish forests could protect red squirrels.

His team combined satellite data with tree species’ location and field data that linked squirrel populations – both red and grey – to different tree types.

Researchers concluded that there are at least 20 existing areas of Scottish forest that could act as safe havens for red squirrels without removing broadleaf trees

‘Great news’ for red squirrel numbers

Professor White described the results as “great news” for red squirrels and the wider environment, as natural strongholds could both conserve squirrel populations and maintain forest diversity.

“Our 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,” he explained.

Grey squirrels and other invasive species

The proliferation of grey squirrels across Britain is a prime example of an invasive species, which can harm the natural resources of an ecosystem.

Invasive species can cause extinction of native plants and animals, reduce biodiversity, compete with native organisms for limited resources, and dramatically alter local ecology.

Even the Arctic is being affected by invasive species. The humble earthworm, which has been reintroduced by humans, is adding to the effects of global warming.

Invasive species are a major threat to ecosystems around the world.

Management of non-native species

Methods for the management and control of invasive species vary across the world - and with mixed results.

Success stories include the restoration of a 10-acre Ravensford wetland site in the Great Smoky Mountains National Park in the US.

This saw the removal of more than 157,000 privet, 1,025 multiflora rose and 540 Japanese honeysuckle plants and the planting of 500 seedlings of native species such as swamp rose, alder and silky willow.

However, Australian efforts to control populations of the non-native cane toad have proved less successful.

Cane toads were introduced to Queensland in the 1930s in an effort to control insect pests on sugar cane crops.

They’ve been spreading west ever since, devastating native species and driving them towards extinction.