The red squirrel (Sciurus vulgaris), also called Eurasian red squirrel, is a species of tree squirrel in the genus Sciurus. It is an arboreal and primarily herbivorous rodent and common throughout Eurasia.
Taxonomy
There have been over 40 described subspecies of the red squirrel, but the taxonomic status of some of these is uncertain. A study published in 1971 recognises 16 subspecies and has served as a basis for subsequent taxonomic work. Although the validity of some subspecies is labelled with uncertainty because of the large variation in red squirrels even within a single region, others are relatively distinctive. At present, there are 23 recognized subspecies of the red squirrel.
A number of subspecies of S. vulgaris have been classified as distinct species. S. v. meridionalis of South Italy was elevated to species status as the Calabrian black squirrel in 2017, which descends from a single source population in central Calabria that became isolated in the Middle Pleistocene. The Japanese squirrel, Sciurus lis, was also historically classified as a subspecies of S. vulgaris, although scientific opinion shifted towards classifying it as a distinct species beginning in the 1960s. The Japanese squirrel likely originated through peripatric speciation from a population of red squirrels that colonized the Japanese archipelago in the Pleistocene and speciated into a distinct population due to the isolation of the islands from the Eurasian mainland, emerging as a recognizable species by the Middle Pleistocene. Genetic studies indicate that another subspecies, S. v. hoffmanni of Sierra Espuña in southeast Spain (below included in S. v. alpinus), may also merit recognition as distinct.
S. v. alpinus. Desmarest, 1822. (synonyms: S. v. baeticus, hoffmanni, infuscatus, italicus, numantius and segurae) Iberian peninsula, southern France, and Italy. Fur is intense russet-brown. S. v. altaicus. Serebrennikov, 1928. Altai region of Russia and Mongolia. Highly variable colouration, including very dark variants. S. v. anadyrensis. Ognev, 1929. Far north of Russia and Siberia. Winter coloration has faint chestnut distributed in the main grey colour. S. v. arcticus. Trouessart, 1906. (synonym: S. v. jacutensis) Boreal Siberia until the Lena River. Fur is red to bay, with a white belly. S. v. balcanicus. Heinrich, 1936. (synonyms: S. v. istrandjae and rhodopensis) Eastern Balkan Peninsula. Fur is brown. S. v. chiliensis. Sowerby III, 1921. Eastern China. Fur is primarily black, with traces of red. S. v. cinerea. Hermann, 1804. S. v. dulkeiti. Ognev, 1929. Amur region of eastern Russia, including the Shantar Islands. Black to dark chestnut fur, with a black tail. S. v. exalbidus. Pallas, 1778. (synonyms: S. v. argenteus and kalbinensis) Western Siberia, east of the Ob River. Light colouration, which becomes pale grey in winter. S. v. fedjushini. Ognev, 1935. Belarus. Body is dark red to brown, tail is dark chestnut or red. S. v. formosovi. Ognev, 1935. Northwest Russia. Winter fur is grey with a chestnut tail. S. v. fuscoater. Altum, 1876. (synonyms: S. v. brunnea, gotthardi, graeca, nigrescens, russus and rutilans) Central Europe. Bright red with a white belly; brown to black populations also present in parts of its range, such as the Danish archipelago. S. v. fusconigricans. Dvigubsky, 1804. Northern Mongolia and China. Summer colouration is dark chestnut to black, winter colouration is black to bluish gray. Belly fur is white in a small area. S. v. leucourus. Kerr, 1792. British Isles. Body fur is red, tail often fades to white over the summer. S. v. lilaeus. Miller, 1907. (synonyms: S. v. ameliae and croaticus). Western Balkan Peninsula. Typically brown. S. v. mantchuricus. Thomas, 1909. (synonyms: S. v. coreae and coreanus). Northeastern China and the Korean Peninsula. Winter fur is dark grey. Tail is black year-round. S. v. martensi. Matschie, 1901. (synonym: S. v. jenissejensis) Western Siberia, west of the Ob River. Summer fur has traces of yellow on the hips. Winter fur is pale gray. Tail is chestnut coloured. S. v. ognevi. Migulin, 1928. (synonyms: S. v. bashkiricus, golzmajeri and uralensis) Western Russia. Small and highly variable in colouration. Winter fur is light gray with traces of buff. S. v. orientis. Thomas, 1906. Ezo Red Squirrel. Hokkaidō, in the Japanese Archipelago. Fur is gray, with a white belly. South of Hokkaidō it is replaced by the Japanese squirrel, Sciurus lis. S. v. rupestris. Thomas, 1907. Sakhalin. Fur is black or dark chestnut, with a black tail throughout the year. S. v. ukrainicus. Migulin, 1928. (synonym: S. v. kessleri) Ukraine. Reddish-brown colour, which is mostly retained during the winter. It is replaced by S. v. fuscoater in the Carpathian Mountains. S. v. varius. Gmelin, 1789. Northern Scandinavia. Winter colouration is light blueish-grey. Tail is chestnut to red. S. v. vulgaris. Linnaeus, 1758. (synonyms: S. v. albonotatus, albus, carpathicus, europaeus, niger, rufus and typicus) Southern Scandinavia. Reddish coloration lacking dark morphs. Tends to be small in size. Population of red squirrels in the island of Bornholm is S. v. vulgaris, but the rest of the Danish archipelago is inhabited by S. v. fuscoater.
Description
The red squirrel has a typical head-and-body length of , a tail length of , and a mass of . Males and females are the same size.
The long tail helps the squirrel to balance and steer when jumping from tree to tree and running along branches, and may keep the animal warm during sleep. It is also used to signal during social interactions.
The dorsal coat color of S. vulgaris is dark but otherwise highly variable. There are several coat colour morphs, ranging through red, reddish-brown, brown, bright chestnut, gray, black, and bluish. Polymorphism is common, although the particular proportions of coat colors vary between different areas. Red coats are most common in Great Britain; in other parts of Europe and Asia different coat colours coexist within populations, much like hair colour in some human populations. Melanism is common, particularly in continental, boreal, and montane populations. Dark coloration is rare in the British Isles. Populations dominated by a single color type are rare and mostly occur on islands.
The underside of the squirrel is always white-cream in colour. The red squirrel sheds its coat twice a year, switching from a thinner summer coat to a thicker, darker winter coat with noticeably larger ear-tufts (a prominent distinguishing feature of this species) between August and November. A lighter, redder overall coat colour, along with the ear-tufts in adults and smaller size, distinguish the red squirrel from the eastern grey squirrel.
The skeleton is physically adapted for climbing and leaping. The red squirrel's bones are relatively light, while the hind legs are disproportionately long and heavy.
Distribution and habitat The red squirrel is found in both coniferous forest and temperate broadleaf woodlands. Red squirrel populations are densest in large areas of coniferous forest, with secondary densities in mixed forests, deciduous forests, and parklands. They can also be found in suburban areas and in conifer plantations.
Red squirrels occupy boreal, coniferous woods in northern Europe and Siberia, preferring Scots pine, Norway spruce and Siberian pine. In western and southern Europe they are found in broad-leaved woods where the mixture of tree and shrub species provides a better year-round source of food. In most of the British Isles and in Italy, broad-leaved woodlands are now less suitable due to the better competitive feeding strategy of introduced grey squirrels.
In Great Britain, Ireland and in Italy, red squirrel populations have decreased in recent years. This decline is associated with the introduction by humans of the eastern grey squirrel (Sciurus carolinensis) from North America. However, the population in Scotland is stabilising due to conservation efforts.
Ecology and behaviour The red squirrel is diurnal; activity typically begins at sunrise, but continues after sunset. Between 60% and 80% of its active period may be spent foraging and feeding.
Red squirrels do not hibernate. During the winter, however, they may remain within their nest for several days during severe weather.
Movement on the ground alternates between series of leaps and alert postures, during which the squirrel sits upright with erect ears while sniffing the air. Movement in trees is rapid and agile, and squirrels may leap between distinct trees up to four meters apart. Climbing down trees is done headfirst, with frequent pauses.
Diet
The red squirrel eats mostly the seeds of trees, especially conifers, neatly stripping cones to get at the seeds within,Krauze-Gryz DAGNY, Gryz, JAKUB. 2015. A review of the diet of the red squirrel (Sciurus vulgaris) in different types of habitats. Red squirrels: ecology, conservation & management in Europe. European Squirrel Initiative, Stoneleigh Park, Warwickshire CV8 2LG, England, pp.39-50. alongside acorns and nuts. Other food sources include fruits and berries, fungi, lichens, young plant shoots, vegetables, garden flowers, and tree sap.Forestry Commission – Red Squirrels . Forestry.gov.uk. Retrieved on 25 July 2013.
More rarely, red squirrels may also eat invertebrates, bird eggs, or nestlings. A Swedish study shows that out of 600 stomach contents of red squirrels examined, only four contained remnants of birds or eggs.
Excess food is put into caches called "middens", either buried or in nooks or holes in trees, and eaten when food is scarce. Caching occurs most frequently during the fall to create food stores for the winter. Although the red squirrel remembers where it created caches at a better-than-chance level, its spatial memory is substantially less accurate and durable than that of grey squirrels. This scatter-hoarding behavior is more commonly observed in deciduous forests than in coniferous ones. Caching is done most frequently with hard, low-perishability foods such as nuts, acorns, and conifer cones, but fungi are sometimes also stored in trees.
Territoriality and nesting Red squirrels make dreys (nests) out of twigs in a branch-fork, forming a domed structure about in diameter. This is lined with moss, leaves, grass, and shredded bark. Tree hollows and woodpecker holes are also used. Dreys are typically built close to the trunk or in a fork of the branches, and are usually at least six meters above the ground. Individual squirrels frequently build multiple dreys and move between them on consecutive nights.
The red squirrel is a solitary animal and is shy and reluctant to share food with others. However, outside the breeding season and particularly in cold months during the winter and spring, several adult squirrels may share a drey to keep warm. Social organization is based on dominance hierarchies within and between sexes; although males are not necessarily dominant to females, the dominant animals tend to be larger and older than subordinate animals, and dominant males tend to have larger home ranges than subordinate males or females. Scent markings are left on trees by rubbing with facial glands, usually at habitual sites. Urine is also used for this purpose. These scent marks serve as both marks of occupied territory and to signal the squirrel's social status and reproductive condition.
Aggressive confrontations between red squirrels typically involve loud calls, foot stamping, and flagging motions with the tail. These may progress into rapid chases and tail-biting.
Typical range size among red squirrels is highly variable, although males tend to maintain larger territories than females. Overlap between territories is common at their edges, particularly when food is abundant, but may be small. Females tend to contract their range when nursing young.
Reproduction