Discover the Only Two Squirrel Species in the United Kingdom and Where They Are Most Commonly Seen

Close up of grey and red squirrels in autumn, UK.
Giedriius/Shutterstock.com

Written by Deniz Martinez

Updated: October 25, 2023

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The United Kingdom is home to just two squirrel species: the Eurasian red squirrel (Sciurus vulgaris) and the eastern grey squirrel (Sciurus carolinensis). Both species share similar life histories, including being arboreal and omnivorous and breeding twice a year. Both species are also active year-round, although less so during the winter. However, while the former species was once widespread across U.K. forests, the latter species is now far more commonly seen across much of the country. Read on to find out why.

Close up of grey and red squirrels in autumn, UK.

Both the Eurasian

red squirrel

and the eastern gray squirrel call the United Kingdom home.

The Eurasian Red Squirrel: The Native Species

Red Animals - Red Squirrel

Once a common sight across U.K. woodlands, the Eurasian red squirrel is becoming increasingly scarce.

The Eurasian red squirrel is the U.K.’s only native squirrel species, with a record going back to the end of the last ice age. Red squirrels can live in coniferous, deciduous, and mixed woodlands. While they aren’t picky about the exact type of forest, however, they still need sufficient amounts of undisturbed habitat to thrive. As it turns out, they have been less adaptable to human development than their gray squirrel cousins.

The Eastern Gray Squirrel: An American Import

Eastern Grey Squirrel on branch.  Scientific name:  Sciurus carolinensis.

The eastern gray squirrel is a common sight in tree-lined suburban and urban areas.

The eastern gray squirrel is a familiar sight to many across the eastern United States. This is because that is actually its native range. However, these squirrels were imported to the U.K. in the 1870s as an ornamental species to populate garden estates. Unfortunately, from these introductions, many escaped into the wild. They were then able to easily adapt to their adopted home’s lowland forests and reproduced quickly. And, just like in the U.S., they have also been able to readily adapt to human-altered landscapes. Gray squirrels are now seen across much of the U.K. in parks and gardens, suburban yards, and even urban areas with at least some trees around for food and shelter.

From Red to Gray Across the U.K.

The red squirrel population in the United Kingdom has collapsed in recent decades in tandem with the gray squirrel population explosion.

The introduction of the gray squirrel turned out to be a disaster for the native red squirrel. As gray squirrel populations have increased and expanded, so too have red squirrel populations decreased and contracted. As a result, the Eurasian red squirrel is currently classified as Endangered in the U.K., while the eastern gray squirrel is classified as Invasive.

Current estimates place the U.K.’s gray squirrel population at around 2.7 million. In contrast, the red squirrel population has plummeted to just 287,000. Furthermore, 75% of that remaining population lives in Scotland, the species’ last remaining stronghold outside of Ireland on the British Isles. Smaller red squirrel populations also persist in other northern areas, on islands, and in remote pockets elsewhere in the country.

As seen on the map above, there are areas where the two populations still overlap. However, whenever the two species meet, the gray squirrel eventually wins out. This is because the gray squirrels have a number of advantages over their red squirrel cousins. First off, they are bigger. Second, they are more tolerant of human development. Third, they have a higher tolerance to tannins. This means they can eat nuts before they’re ripe, while red squirrels must wait. And fourth and most alarming, gray squirrels carry a virus known as squirrelpox that is transmissible to red squirrels. While the gray squirrel carriers are immune, it has proven fatal to red squirrels.

How To Tell Reds and Grays Apart – Don’t Just Count on Color!

Black Squirrel

Melanin mutations can impact both “red” squirrels and “gray” squirrels, making their coat colors range from black (melanistic) to white (leucistic or albino).

While it may seem at first that you could simply tell the red and gray squirrel species apart by their respective fur colors, don’t let their common names fool you. While it is true that red squirrels are usually red and gray squirrels are usually gray, both grayish red squirrels and reddish gray squirrels are not uncommon. Furthermore, either species can have coat colors that can vary from white, brown, red, gray, and black. This is because both species get their fur colors from melanin pigments — just like all other mammals, including us humans!

While color may not in and of itself be a reliable identification tool, other differences can be used to help tell native red squirrels and non-native gray squirrels apart:

Ear Tufts

Red Squirrel Photo North Yorkshire Eat Swim Jump Reflection Pool

A red squirrel’s ear tufts can make it look like it has mini horns.

Most notably, only red squirrels have those cute ear tufts. However, these are shed down in the summer. Gray squirrels, on the other hand, are tuftless year-round.

Tails

A grey squirrel with a bushy tail perching on a fence post against a defocused background.

Gray squirrels usually have tail hairs that are banded with color, including white tips.

Red squirrels also have a fairly uniform tail color. In contrast, gray squirrel tails generally look more multicolored.

Overall Size and Weight

Lastly, red squirrels are also markedly lighter and smaller than their gray squirrel cousins. While red squirrels weigh in at only 9 – 12 ounces, gray squirrels are plumper at 14 – 21 ounces. Likewise, red squirrels only grow to a length of 7.5 – 9 inches plus a tail length of 6 to 8 inches, while gray squirrels can grow to a length of 9.1 – 11.8 inches plus a tail length of 7.5 – 9.8 inches.

Summary of Discover the Only Two Squirrel Species in the United Kingdom and Where They Are Most Commonly Seen

Eurasian Red SquirrelEastern Gray Squirrel
status in the United Kingdomnative species; classified as Endangerednon-native species, introduced from the U.S. in the 1870s; classified as Invasive
range & distributionrange contracting since gray squirrel introduction, now mostly confined to the north, islands, and remote pockets elsewhererange continually expanding since its introduction in the late 19th c., now widespread across most of the U.K.
population287,000 (about 75% in Scotland)2.7 million
habitatconiferous, deciduous, and mixed woodlandsdeciduous and mixed woodlands; also parks and gardens, suburban yards, and urban areas with trees
sizesmaller; head-and-body length of 19 – 23 cm (7.5 – 9 in), tail length 15 – 20 cm (6 to 8 in), mass 250 – 340 g (9 – 12 oz)larger; head-and-body length 23 – 30 cm (9.1 – 11.8 in), tail length 19 – 25 cm (7.5 – 9.8 in), mass 400 – 600 g (14 – 21 oz)
colorusually rusty red but can vary based on age, seasons, and geneticstypically gray but can vary based on age, seasons, and genetics; white and black morphs more common than in red squirrels
ear tuftspresent (shed during summer)absent
tailuniform colorbands of colors, often with white tips


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About the Author

Deniz Martinez is a writer at A-Z Animals where her primary focus is on biogeography, ornithology, and mammalogy. Deniz has been researching, teaching, and writing about animals for over 10 years and holds both an MS degree from American Public University earned in 2016 and an MA degree from Lindenwood University earned in 2022. A resident of Pennsylvania, Deniz also runs Art History Animalia, a website and associated social media dedicated to investigating intersections of natural history with art & visual culture history via exploring animal iconography.

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