Eurasian Red Squirrel

The Eurasian red squirrel (Sciurus vulgaris) is a small tree squirrel distributed from western Europe across northern Asia to the Pacific coast. Adults have a head-and-body length of about 20–25 cm, with a 15–20 cm bushy tail. Coat colour varies remarkably, from bright red through brown and grey to almost black, while the belly remains white. The winter coat is thicker and often greyer, and the prominent ear tufts are most developed in winter.

The large tail acts as a counterbalance when the squirrel runs and jumps through branches and can also be wrapped around the body for insulation while resting. Curved claws and powerful hind limbs allow rapid climbing in both directions along trunks and branches.

Red squirrels inhabit coniferous, deciduous and mixed forests as well as wooded parks and large gardens. Habitat quality depends strongly on the supply and distribution of seed-producing trees, and squirrels shift their use of the landscape as the best feeding patches change through time.

Conifer forests can support high densities where spruce or pine crops are reliable, while broadleaved woodland provides foods such as hazelnuts and other tree seeds. A structurally varied canopy, mature seed-producing trees and connected woodland all help squirrels move efficiently between feeding and nesting areas.

Tree seeds are the main food, but the exact diet changes strongly with season, forest type and annual seed crops. Spruce and pine seeds, hazelnuts and other tree seeds are especially important, while buds, shoots, berries, fruit and fungi are also eaten. Animal food such as insects, eggs or nestlings is taken occasionally but forms a small part of the normal diet.

Red squirrels make many small, scattered food stores for periods when fresh supplies are scarce. Nuts and seeds are hidden individually in the ground, beneath leaf litter or in other concealed places. Field experiments show that spatial memory helps red squirrels relocate stored food, although their memory was less persistent than that of grey squirrels tested in the same way.

Stored food is far from guaranteed to remain available. A field experiment in an urban park in Warsaw found that about half of cached hazelnuts disappeared within one day, and after 50 days only around 1% were expected to remain. Stores can therefore be recovered by the squirrel, stolen by other animals or simply remain where they were hidden.

Fungi are also cached. In British conifer plantations, red squirrels have been observed placing mushroom fruiting bodies on tree branches, apparently allowing them to dry before later consumption. Most of these stores disappeared within two weeks.

Food that is never recovered can also disperse seeds, although the importance varies greatly among plant species. In a study of Korean pine, red squirrels cached an estimated 65% of the mature seeds outside the pine stand, and seedlings were found as far as 600 m from their parent trees. In that forest system the squirrel therefore acts as an effective seed disperser.

Red squirrels are diurnal and mostly solitary. Activity is often greatest in the morning and later afternoon. They do not hibernate, but prolonged rain, strong winds or severe winter weather can keep them inside their dreys for extended periods.

Much of the active day is spent moving between feeding sites in the canopy and on the ground, with squirrels adjusting their routines quickly as seed crops and other food sources change.

Red squirrels use overlapping home ranges rather than rigid exclusive territories, particularly between males and females. Studies using radio tracking show that male ranges are generally larger than female ranges and often expand in spring and early summer, when males search widely for receptive females. Females use smaller, more intensively occupied core areas.

A study in northern England showed how closely space use follows food. In conifer plantations where seed crops were patchy and changed through time, squirrels shifted among several separate feeding areas, and females used larger home ranges where food was poorer. Dominant females may still defend core areas from other females even though the broader ranges overlap.

Breeding is closely linked to food availability and female condition. Females may produce one or two litters in a year, with mating activity often concentrated in late winter and again in spring or early summer when conditions allow. When a female enters oestrus, several males may converge on her home range and pursue her in fast mating chases through the trees.

A long-term study followed reproduction through 18 breeding seasons in coniferous forest and 16 in deciduous woodland. Food abundance and female density both influenced how many females successfully raised young. In poor food years some females may skip breeding, while rich seed crops allow more females to reproduce.

After a gestation of about 38–39 days, the female gives birth in a spherical drey built from twigs, leaves, moss and other vegetation. Litter size generally ranges from one to six young, while seven has been documented as an exceptionally large litter. The young are born blind and hairless, begin leaving the nest after roughly six weeks and are normally weaned by around 8–10 weeks. The female provides all parental care.

Introduced eastern grey squirrels (Sciurus carolinensis) have replaced red squirrels over large areas of Britain and parts of Italy, but the process is not simply one species directly driving the other away. A systematic review published in 2023 found that the speed and mechanism of replacement vary with habitat and food. In some conifer forests adult red squirrels persisted despite high grey-squirrel numbers, while far fewer young red squirrels established themselves; replacement has generally been faster in broadleaved habitats.

In Britain the interaction is intensified by squirrelpox virus. Grey squirrels can carry the virus with little apparent illness, whereas infection is often lethal to red squirrels. The virus is not necessary for grey squirrels to replace reds, but modelling studies included in the 2023 review found that it can make the replacement process up to 25 times faster. Squirrelpox has not played the same role in Italy, showing how different mechanisms can dominate in different regions.

Squirrels have a distinctive place in Norse mythology through Ratatoskr, the squirrel associated with the world tree Yggdrasil. It runs up and down the trunk carrying messages between the eagle in the crown and the serpent Níðhöggr at the roots, giving the squirrel a lasting and distinctive place in Nordic culture.

The Eurasian red squirrel is classified as least concern on the IUCN Red List. It remains widespread across a vast Palearctic range from Europe to the Russian Far East.

Local abundance can fluctuate strongly with tree-seed crops and forest conditions. The much more serious regional declines in Britain and parts of Italy are driven by competition and other interactions with introduced grey squirrels rather than by a similar decline across the species’ full range.