Threats to the Red Squirrel

Once common, red squirrels have declined rapidly since the 1950s.

Numbers in the UK have fallen from around 3.5 million, to a current estimated population of around 120,000.

In Wales, there are only three remaining red squirrel populations: in Anglesey, around the Tywi Forest in mid Wales and in the Clocaenog Forest in north eastern Wales.

In 2009, a Conservation plan for Red Squirrels in Wales was approved by the Welsh Government.

The plan pinpointed the Tywi Forest area in mid Wales as one of three focal sites for urgent strategic action for red squirrel conservation.

Map of red squirrel distribution in Wales

Map of red squirrel distribution in Wales


Habitat destruction and fragmentation

A significant decline in broadleaved tree cover, increased fragmentation of woodlands and overgrazing, causing a reduction in regeneration, all contributed to the decline of red squirrels in the 19th century.

This however cannot fully explain the collapse in red squirrel numbers in the UK. Ironically, the more recently planted conifer woods do, in fact, provide some new suitable food resources for reds and may also aid their future conservation.

Edge of Twyi Forest

Edge of Twyi Forest

Competition from grey squirrels

Red squirrels are under increasing pressure from non-native grey squirrels. The grey squirrel was introduced to the UK in the 1870s. Since the introduction of a handful of animals, grey squirrel numbers have climbed to more than 3 million.

Grey squirrels have replaced red squirrel populations throughout much of their former range; greys can colonise woodlands at a rate of 6 miles per year and reds commonly disappear within 15 years of the arrival of greys to an area.

Grey squirrel on log by Gillian Day

Grey squirrel on log by Gillian Day

The greys don’t actually drive reds out or attack them; however, the presence of greys often means reds do not have enough to eat. Greys, unlike reds, having originated from hickory and oak woodlands of eastern North America, are better able to digest acorns, coping better with the high concentrations of toxic tannins that they contain. In broadleaf woodlands therefore, greys dominate food resources.

This competitive exclusion from food sources causes weight loss in the red squirrel, reducing their chances of surviving the winter and of breeding successfully. The grey squirrel is much larger than the red. Their extra body weight means that they can store three to four times more fat than red squirrels and so have a better chance of surviving the winter.

Greys also produce more young than reds and live at higher densities (more squirrels per hectare) making them a stronger contender in the survival stakes. Although the grey squirrel has the advantage over reds in broadleaf woodlands, they are less able to dominate in coniferous woods.

Here reds can eat the small seeds of the coniferous trees, which do not provide enough nutrition for the larger greys and so enable their survival in this habitat. Reds favour particular species within conifer forests: Norway spruce, Scot’s pine, Japanese larch and Lodgepole pine are all useful food sources for red squirrels, but these species are at low density within the Sitka-dominated plantations and do not produce cones every year. This means that even though the conifer habitat area in mid Wales is large, only a very small area will be optimal for reds at any one time.

Changes in red squirrel distribution since 1945

Changes in red squirrel distribution since 1945.  Janet Wickens, 2014. Red Squirrel Survival Trust.


Red squirrels are at risk from the deadly Squirrelpox virus (parapox), capable of devastating red squirrel populations. The Squirrelpox virus can be carried by grey squirrels without causing them harm, but red squirrels have no immunity. Once infected, reds will die within a matter of weeks, or even days; there is no known cure. Infected squirrels may be lethargic and shivering with scabs or lesions around the eyes and nose.


Squirrelpox, Sarah McNeil