The grey squirrel (Sciurus carolinensis) is a rodent native to North America, brought to Italy by humans. Curious, not very wary and easy to see in parks, it seems like a charming guest. In reality it is one of the most studied invasive alien species in Europe, because wherever it spreads it tends to replace our native red squirrel.
How to recognise the grey squirrel
It belongs to the order Rodentia and the family Sciuridae. It has a sturdy, medium-sized build: it is about 40-50 cm long in total, almost half of which is tail, and weighs about 400-800 grams. The back is ash grey, with reddish tones on the legs, head and flanks, while the belly is white or pale grey. The tail is very bushy, grey and fringed with white.
Differences from the red squirrel
Unlike the red squirrel, it has no ear tufts and is larger and heavier. Colour alone is not enough, because a red squirrel can also have a grey or dark coat, and the grey squirrel can have reddish tones: it is best to look at the ears, the build and the white fringe of the tail.
How it reached Italy and where it lives
It was introduced by humans into parks, precisely because it was ornamental and not very wary. The first introduction dates back to 1948, with two pairs released in a park at Candiolo, near the Stupinigi woods (Turin). In 1966 more animals were released at Genoa Nervi, and in 1999 another major introduction was reported in the Ticino Valley.
Today it is found mainly in Piedmont, Lombardy and Liguria, with a population in Umbria too, around Perugia. It frequents broadleaved woodland, urban parks and gardens. If you live near a park, keep your eyes open, because I once found one in my vegetable garden, on a small bare tree!
Habits and diet
It is a diurnal animal: in winter it is active mainly in the warmest hours, around midday, and in summer in the morning or towards sunset, when it is cooler. It feeds mainly on acorns, nuts and other seeds, as well as buds, berries and fungi, and occasionally on insects, eggs and nestlings. Like the red squirrel, it hides some of its food to build up reserves.
In the wild most individuals live only a few years, although the maximum recorded in the wild is about 12 years.
Reproduction and nest
It nests in tree hollows or in round nests built from leaves and twigs. After a gestation of about 44 days the female usually gives birth to 2-4 young, naked and blind, and can do so once or twice a year. The young become independent at around 12 weeks.
Why is the grey squirrel a problem?
It does not attack the red squirrel, but it beats it in the competition for food and space, partly because it makes better use of seeds such as acorns. It can also carry a virus, the parapoxvirus, which is often fatal to the red squirrel. In Piedmont the red squirrel has already disappeared from more than 1,600 km² of land. The grey squirrel can also damage woods and plantations by stripping bark from trees.
This is why since 2016 it has been on the European list of invasive alien species of Union concern, subject to the rules of EU Regulation 1143/2014, and since 2023 Italy has had national measures to manage it. The subject is debated: control also involves removing the animals, while some associations call for non-lethal methods. One simple rule applies to everyone: animals should never be released into the wild.
Introduced to decorate our parks, it now endangers a species that belongs in our woods. Was it worth it? You can find more encounters with wildlife in my gallery of animals.
