2008/9 Schools Wikipedia Selection. Related subjects: Mammals
Red squirrel range
The red squirrel or Eurasian red squirrel (Sciurus vulgaris) is a species of tree squirrel ( genus Sciurus). The red squirrel is a tree-dwelling omnivorous rodent that is common throughout Eurasia. In Britain, however, numbers have decreased drastically, in part due to the introduction of the eastern gray squirrel from North America and in part through poor management of its woodland habitat.
The red squirrel has a typical head-and-body length of 19 to 23 cm (7.5 to 9 in), a tail length of 15 to 20 cm (5.9 to 7.9 in) and a mass of 250 to 340 g (8.8 to 12 oz). It is not sexually dimorphic, as males and females are the same size. The red squirrel is slightly smaller than the eastern grey squirrel which has a head-and-body length of 25 to 30 cm (0.8 to 1 oz) and weighs between 400 and 800 g (14 oz to 1.8 lb). It is thought that 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.
The coat of the red squirrel varies in colour with time of year and location. There are several different coat colour morphs ranging from black to red. Red coats are most common in Great Britain; in other parts of Europe and Asia the different coat colours co-exist within populations, much like hair colour in humans. 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 larger ear-tufts, helps to distinguish the European red squirrel from both the eastern grey squirrel or the American red squirrel.
The red squirrel, like most tree squirrels, has sharp, curved claws to enable the climbing of trees, even when branches are overhanging.
Reproduction and mortality
Mating can occur in late winter during February and March and in summer between June and July. Up to two litters a year per female are possible. Each litter usually contains three or four young although as many as six may be born. Gestation is about 38 to 39 days. The young are looked after by the mother alone and are born helpless, blind and deaf and weigh between 10 and 15 g. Their body is covered by hair at 21 days, their eyes and ears open after three to four weeks, and they develop all their teeth by 42 days. Juvenile red squirrels can eat solids around 40 days following birth and from that point can leave the nest on their own to find food; however, they still suckle from their mother until weaning occurs at 8 to 10 weeks.
During mating, males detect females that are in œstrus by an odour that they produce, and although there is no courtship the male will chase the female for up to an hour prior to mating. Usually multiple males will chase a single female until the dominant male, usually the largest in the group, mates with the female. Males and females will mate multiple times with many partners. Females must reach a minimum body mass before they enter œstrus, and heavy females on average produce more young. If food is scarce breeding may be delayed. Typically a female will produce her first litter in her second year.
The lifespan of the red squirrel is on average 3 years, although individuals may reach 7 years of age, and 10 in captivity. Survival is positively related to availability of autumn–winter tree seeds; on average, 75–85% of juveniles disappear during their first winter, and mortality is approximately 50% for winters following the first.
Ecology and behaviour
The red squirrel is native to coniferous forest and is also found in temperate broadleaf woodlands. The squirrel makes a nest known as a drey in a branch-fork of a conifer by laying down twigs to make a domed structure about 25 to 30 cm in diameter, then lining it with moss, leaves, grass and bark. Hollows and woodpeckers' nests are also used. 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 winter, multiple red squirrels may share a drey to keep warm. Social organization is based on dominance hierarchies among 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.
The red squirrel eats mostly the seeds of trees, neatly stripping conifer cones to get at the seeds within. Fungi, birds' eggs, berries and young shoots are also eaten. Often the bark of trees is removed to allow access to sap. Between 60% and 80% of its active period may be spent foraging and feeding. Excess food is put into caches, either buried or in nooks or holes in trees, and eaten when food is scarce. 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 squirrel; it therefore will often have to search for them when in need, and many caches are never found again. No territories are maintained, and the feeding areas of individuals overlap considerably.
The active period for the red squirrel is in the morning and in the late afternoon and evening. It often rests in its nest in the middle of the day, avoiding the heat and the high visibility to birds of prey that are dangers during these hours. During the winter, this mid-day rest is often much more brief, or absent entirely, although harsh weather may cause the animal to stay in its nest for up to days at a time.
Arboreal predators include small mammals including the pine marten, wild cats, and the stoat, which preys on nestlings; birds, including owls and raptors such as the goshawk and buzzards, may also take the red squirrel. The red fox, cats and dogs can prey upon the red squirrel when it is on the ground. Humans influence the population size and mortality of the red squirrel by destroying or altering habitats, by causing road casualties, and by controlling populations by hunting.
The red squirrel collects mushrooms and dries them in trees.
The red squirrel is protected in most of Europe, as it is listed in Appendix III of the Bern Convention; it is also listed as Near Threatened on the IUCN Red List. In some areas it is abundant and is hunted for its fur. Although not thought to be under any threat worldwide, the red squirrel has drastically reduced in number in the United Kingdom. Fewer than 140,000 individuals are thought to be left , approximately 85% of which are in Scotland. This population decrease is often ascribed to the introduction of the eastern gray squirrel from North America, but the loss and fragmentation of its native woodland habitat has also played a major role.
In order to conserve the remaining numbers of the red squirrel, the UK government in January 2006 announced a mass culling program for the eastern gray squirrel. This was welcomed by many conservation groups. An earlier cull of the eastern gray squirrel began in 1998 on the North Wales island of Anglesey. This facilitated the natural recovery of the remaining red squirrel populations and has been followed by the successful reintroduction of the red squirrel into Newborough Forest. The UK has established a local program known as the "North East Scotland Biodiversity Partnership", an element of the national Biodiversity Action Plan. This program is administered by the Grampian Squirrel Society, with an aim of protecting the red squirrel; the program centers on the Banchory and Cults areas.
There are also several local conservation groups in the UK, for example, the Red Squirrel Conservation group in Mallerstang, Cumbria.
Outside the UK and Ireland, the threat from the eastern gray squirrel comes from a population in Piedmont, Italy, where two pairs escaped from captivity in 1948. A significant drop in red squirrel populations in the area has been observed since 1970, and it is feared that the eastern gray squirrel may expand into the rest of Europe.
The eastern gray squirrel population appears to be able to out-compete the red squirrel for various reasons:
- The eastern gray squirrel can easily digest acorns, while the red squirrel cannot.
- The eastern gray squirrel carries a disease, the squirrel parapoxvirus, that does not appear to affect their health but will often kill the red squirrel.
- When the red squirrel is put under pressure, it will not breed as often.
It is worth noting that the eastern gray squirrel and the red squirrel are not directly antagonistic towards each other, and direct violent conflict between these species is not a factor in the decline in red squirrel populations.
Research undertaken in 2007 in the UK credits the Pine Marten with reducing the population of the invasive eastern gray squirrel in the UK. Where the range of the expanding Pine Marten population meets that of the Gray Squirrel, the population of these squirrels retreats. It is theorised that because the gray squirrel spends more time on the ground than the red, that they are far more apt to come in contact with this predator.
Cultural and economic significance
In Norse mythology, Ratatosk is a red squirrel who runs up and down with messages in the world tree, Yggdrasill, and spreads gossip. In particular, he ferried insults between the eagle at the top of Yggdrasill and the dragon Níðhöggr beneath its roots.
The red squirrel used to be widely hunted for its pelt. In Finland squirrel pelts were used as currency in ancient times, before the introduction of coinage. The expression "squirrel pelt" is still widely understood there to be a reference to money.
On the island of Anglesey, red squirrel conservation forms part of a broader socio-economic project managed by Menter Mon. An island-wide cull of gray squirrels has entered the final stage, and the red squirrel is now being reintroduced across the full spectrum of habitats within which it was once found. Some of the released animals can be watched via a live-feed webcam.
Taxonomy and distribution
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.
- S. v. altaicus Serebrennikov, 1928
- S. v. anadyrensis Ognev, 1929
- S. v. argenteus Kerr, 1792
- S. v. balcanicus Heinrich, 1936
- S. v. bashkiricus Ognev, 1935
- S. v. fuscoater Altum, 1876
- S. v. fusconigricans Dvigubsky, 1804
- S. v. infuscatus Cabrera, 1905
- S. v. italicus Bonaparte, 1838
- S. v. jacutensis Ognev, 1929
- S. v. jenissejensis Ognev, 1935
- S. v. leucourus Kerr, 1792
- S. v. mantchuricus Thomas, 1909
- S. v. meridionalis Lucifero, 1907
- S. v. rupestris Thomas, 1907
- S. v. vulgaris Linnaeus, 1758