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| 질의: mammal | 결과: 1834번째/3447 | |
Eurasian Red Squirrel (Sciurus vulgaris) - Wiki
| 제목: | Eurasian Red Squirrel (Sciurus vulgaris) - Wiki
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Red Squirrel
From Wikipedia, the free encyclopedia
[Photo] Sciurus vulgaris (English: Red Squirrel, Polski: Wiewi??rka pospolita). Date 2004-04-20. Author Andrzej Barabasz (http://commons.wikimedia.org/wiki/User:Chepry)
The red squirrel or Eurasian red squirrel (Sciurus vulgaris) is a species of tree squirrel (genus Sciurus). Red squirrels are tree-dwelling omnivorous rodents that are frequently found throughout Eurasia. In Britain, however, numbers have decreased drastically due to the introduction of the eastern grey squirrel from North America.
Physical description
Red squirrels have a typical head to body length of 19 to 23 cm, a tail length of 15 to 20 cm and a mass of 250 to 340 g. They are 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 to body length of 25 to 30 cm and weighs between 400 and 800 g. 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. Red squirrels shed their coats 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 either of 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 to 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. The juvenile red squirrel 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 eight to 10 weeks.
During mating, males detect females that are in œstrus from an odor 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 three 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 mortaility is approximately 50% for winters following the first.
Ecology and behaviour
The red squirrel is native to usually coniferous forest and it 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 woodpecker's nests are also used. Red Squirrels are solitary animals and are 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.
Red squirrels eat 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 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 red squirrels do remember where they created caches at a better than chance level, their spatial memory is substantially less accurate and durable than that of grey squirrels; they 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 late afternoon-evening. They often rest in their nests 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 goshawk and buzzard may also take red squirrels. The red fox, cats and dogs can prey upon the red squirrel when they are on the ground. Humans influence the population size and mortality of the red squirrel by destroying or altering habitats, causing road casualties, or through controlling populations by hunting.
The Red Squirrel collects mushrooms and dries them in trees.
Conservation
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 hunted for its fur. Although not thought to be under any threat worldwide, the red squirrel has drastically reduced in numbers in the United Kingdom. Under 140,000 individuals are thought to be left, approximately 85% of which are in Scotland. This population decrease is likely to be due to the introduction of the eastern grey squirrel from North America as well as the loss and fragmentation of its native woodland habitat.
In order to conserve remaining numbers of red squirrels, the UK Government in January 2006 announced a mass culling program for grey squirrels. This was welcomed by many conservation groups. An earlier cull of grey squirrels began in 1998 on the North Wales island of Anglesey. This facilitated the natural recovery of the remaining red squirrels populations and has been followed by the successful reintroduction of red squirrels back 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 of the UK and Ireland, the threat from eastern grey squirrels 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 eastern grey squirrels may expand into the rest of Europe.
The eastern grey squirrel population appears to be able to out-compete the red squirrel for various reasons:
The eastern grey squirrel can easily digest acorns, while the red squirrel cannot.
The eastern grey squirrel carries a disease, the squirrel parapoxvirus, that does not appear to affect their health, though will kill most red squirrels.
When red squirrels are put under pressure, they will not breed as often.
It is worth noting that eastern grey squirrels do not usually attack red squirrels, and direct violent conflict between these species is not a factor in the decline in red squirrel populations.
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 N??ðh??ggr beneath its roots.
Red squirrel used to be widely hunted for its pelt. In Finland squirrel pelts were used as money in the ancient times, before the introduction of currency. The expression "squirrel pelt" is still widely understood to be a reference to money.
On the island of Anglesey, red squirrel conservation forms part of a broader socio-ecomomic project managed by Menter Mon. An island wide cull of grey squirrels has entered a final stage, and red squirrels are now being reintroduced back across the full spectrum of habitats within which they were once found. Some of the released animals can be watched via a live-feed webcam: Red squirrel webcam http://www.redsquirrels.info/squirrelcam.html
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http://en.wikipedia.org/wiki/Red_Squirrel
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