Q&A: Why are red squirrels endangered—and can we save them?

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The red squirrel was once a familiar sight across Britain. Today, it has disappeared from much of its former range.

Kat Hamill, senior lecturer in zoology at Nottingham Trent University, explains what has happened to one of Britain's most recognizable native mammals—and whether science and conservation can help bring it back. The Eurasian red squirrel (Sciurus vulgaris) is the U.K.'s only native squirrel species. It was once widespread across England, Scotland, Wales and Ireland, with historical populations estimated to number in the millions.

Today, red squirrels have disappeared from as much as 95% of their former range in England. Scotland is now home to around 75% of Britain's remaining red squirrels, with smaller populations surviving in northern England, parts of Wales and Northern Ireland, and on a handful of offshore islands including the Isle of Wight and Brownsea Island. There are estimated to be around 287,000 red squirrels left in Britain, fewer than 40,000 of them in England.

The species is classified as endangered in England and Wales and near threatened in Scotland on the Red List for Britain's Terrestrial Mammals. The biggest change came with the introduction of eastern gray squirrels (Sciurus carolinensis) from North America in the late 19th century. Gray squirrels spread rapidly across Britain, and there are now estimated to be around 2.7 million.

Red and gray squirrels have similar requirements, with around 70% overlap in their ecological niches. This means they often compete for the same food and space. They are larger and can make better use of a wider range of food, particularly in broadleaf woodland.

This can allow them to outcompete red squirrels for resources. Gray squirrels can carry squirrelpox virus without being seriously affected by it. For red squirrels, however, infection can be devastating.