Eurasian squirrel

from Wikipedia, the free encyclopedia
Eurasian squirrel
Red squirrel (Sciurus vulgaris)

Red squirrel ( Sciurus vulgaris )

Systematics
Subordination : Squirrel relatives (Sciuromorpha)
Family : Squirrel (Sciuridae)
Subfamily : Tree squirrel and flying squirrel (Sciurinae)
Tribe : Tree squirrel (Sciurini)
Genre : Red squirrel ( Sciurus )
Type : Eurasian squirrel
Scientific name
Sciurus vulgaris
Linnaeus , 1758

The Eurasian squirrel ( Sciurus vulgaris ), often only as squirrels known, a rodent from the family of squirrel (Sciuridae). It is the only member of the squirrel genus that occurs naturally in Central Europe and is also known as the European squirrel to distinguish it from other species such as the Caucasian squirrel and the gray squirrel , which is naturalized in Europe .

Regional names of the animal are Eichkitten, Eichkatz (er) l, Eichkater, moreover - implemented from the respective dialect form - Eicher (left) (Switzerland), Eichhase (Austria), Baumfuchs (Hessen), Konradchen (Nassau), Eichhalm (Württemberg) as well as in Low German Katteker (Katzeicher) and Ekenaape (oak monkey) . For the not fully clarified origin of the word see article squirrel .

features

Build and dimensions

Squirrel on a path post

In its physique, the squirrel is adapted to a tree-dwelling and climbing way of life. It has a mass of around 200–400 g. The head body length is 20-25 cm. The two-line hairy, bushy tail is 15–20 cm long. It serves as a balancing aid when climbing and as a rudder when jumping. The tail is always kept in the air when running. The sexes cannot be distinguished on the basis of size and coat color.

The strong claws help squirrels climb

Squirrels are one of the sole walkers . They have four long, very mobile fingers on their front paws, equipped with long, curved claws; the stunted thumbs also have claws. The hind legs are disproportionately long and very strong. The long, curved claws give the squirrels a good grip even when climbing upside down on smooth trunks.

skull

Skull ( Museum Wiesbaden Collection )

The squirrel's skull is broad, flat and rounded with a high, largely egg-shaped skull and a short, narrow and high snout . Compared to the gray squirrel's skull, the squirrel's skull is smaller, the skull is taller, the postorbital processes are longer and narrower, and the forehead is slightly indented in front between the eye sockets. The squirrel also differs from the Caucasian squirrel in its higher skull and longer snout, the long lower edge of the zygomatic arch , which attaches in the middle to the upper rear molar on the upper jaw, and larger tympanic chambers with two instead of three septum walls. In contrast to the Caucasian squirrel, the width of the lower jaw branch in the middle is greater than the length of the molar row.

Depending on the subspecies, the squirrel's skull dimensions vary across the range. The size of the skull increases from north to south throughout Eurasia, regardless of climatic factors. In Europe, however, this relationship is not very clear, and in Central Europe an increase in size from the south and west to the northeast has been noted. The squirrel's condylobasal length is 44.0–49.3 mm, the basal length 40.2–48.4 mm, the zygomatic width 29.0–35.2 mm, the nasal length 14.0–18.7 mm, and the length the upper molar row 8.5–10.4 mm. In young animals, the skull seems to grow a little beyond the first year. There is no gender dimorphism in terms of skull dimensions.

denture

1 · 0 · 2 · 3  =  22
1 · 0 · 1 · 3
Squirrel tooth formula

The squirrel's teeth, which are typical for croissants, have one incisor tooth , two premolar teeth above and one premolar tooth below, and three molars in each half of the jaw . Canine teeth are absent, the total number of teeth is 22.

The size of the premolar and molar teeth increases from front to back. The anterior upper molar of the squirrel is small, pin-shaped, pushed inwards a little, almost functionless and, unlike in the Caucasian squirrel, always present in both halves of the jaw. The rear upper premolar tooth almost corresponds in shape and size to the upper molars. Like these, it has a large, crescent-shaped hump on the tongue side and four humps on the cheek side. From the higher, second and fourth cusps, transverse ridges extend to the cusp on the tongue side. A well-defined cusp on the posterior molar replaces the ridge otherwise connected to the fourth cusp, and it is absent from the posterior molar. The lower premolar and lower molars are diamond-shaped with a recessed center. They each have a main hump at the four corners. At the front and on both sides there is a small side hump that disappears with increasing wear. Wiltafsky (1978) gives the number of tooth roots in the anterior upper molar tooth with one, in the posterior upper molar tooth, in the upper molars and in the lower molar teeth with three and in the lower molars with four. Niethammer and Krapp (1978) give the number of tooth sockets for the anterior upper premolar tooth, two for the lower premolar, three for the posterior upper premolar, three for the upper molar and the posterior lower molar and four for the anterior and central lower molar .

The upper posterior and lower premolar teeth have precursors in the deciduous dentition that fail at 16 weeks of age. In young animals, the rear upper premolar tooth is much smaller than the molar teeth, its rear edge is always heavily worn, and it forms a chewing surface with the front edge of the anterior upper molar. The wear and tear of the premolar and molar teeth and the growth of the root cement can also be used to determine the age.

Hairiness and coloring

The dense hair is short, silky to coarser (8,000 to 10,000 hairs per cm²). The length of the guard hairs is 3–11 mm on the nose (mean 5.9 mm), on the abdomen 13–23 mm (mean 16.4 mm), and on the back 17–23 mm (mean 22.5 mm). In the hair base, the hair has a diameter of 0.04 mm, in the area of ​​the awn the diameter increases to 0.12 mm. The wool hairs are of different lengths, wavy or spirally wound. Their diameter is 0.010-0.015 mm. They are tapered towards the tip and the hair bulb. The fully grown ear brush hairs are 3–5 cm long, the tail hairs 5–8 cm (occasionally up to 10 cm) long.

The top color varies from light red to brown-black; the ventral side is white or cream-colored, clearly delimited from the fur on the back. The winter fur is much denser than the summer fur. In winter, the coat color often becomes darker and can also take on gray tones. In winter fur, squirrels have red-brown ear brushes up to 3.5 cm long. In the summer coat, these ear brushes are small or nonexistent. In winter, the otherwise bare soles of the feet are also hairy.

  • With summer fur

  • Dark brown color variant

  • In autumn with ear brushes

  • With winter fur

Albinism and melanism are quite common phenomena among squirrels on the European continent.

The squirrel changes its coat twice a year. The hair change in spring runs from the head over the back and the sides of the body to the thighs, the autumn hair change runs in the opposite direction, starting at the base of the tail and moving towards the head. The ears and tail change their hair only once a year. First, in the spring, part of the awns and the entire undercoat of the tail go out. During the summer, the tail hairs renew themselves completely, starting from the middle and ending towards the sides. The ear brush hairs grow from summer to winter. Changing hair in spring takes a little longer than changing hair in autumn. Females begin the spring hair change a little later than the males, when the young are born they have completed it.

distribution and habitat

Habitat of the Eurasian squirrel

The distribution area of ​​the Eurasian squirrel is Palearctic and includes almost all of Europe including Great Britain and Ireland as well as large parts of North Asia from the Urals east to the Pacific coast in Kamchatka , the People's Republic of China and Korea as well as the islands of Sakhalin and Hokkaidō . In Europe it is only missing in south-east England, as well as south-west Spain and south Portugal and in some regions of Italy. The species occurs only sporadically in the Balkans and the squirrel is not found on most of the islands of the Mediterranean Sea. In Turkey , the deposits include the European parts ( Eastern Thrace ) and northeastern Turkey.

Squirrels can be found up to an altitude of 2000 meters, according to other sources up to 3100 meters in the Alps .

The typical habitats, based on the entire distribution area, are predominantly boreal coniferous forests . Only in the European part of the distribution area are squirrels also native to deciduous and mixed forests. As a cultural follower , they are often found there today in parks and gardens.

Way of life

activity

Squirrel climbs upside down
Goblin of a squirrel
Squirrel transports its young in a rigid state

Squirrels are diurnal. The animals climb very skillfully and move forward in jerks, their movements are very quick and precise. It does not matter whether you are climbing a tree trunk or a rough house facade or climbing down headfirst. As they climb down, they turn their rear paws outward and backward. With one jump, the animals can easily cover distances of four to five meters. Because of their low weight, squirrels also dare to climb very thin branches, always jumping forward and are therefore absolutely superior to any pursuer. They also move in jumps on the ground, not at a gallop like other four-legged friends; they are relatively slow and can easily be grabbed by dogs and cats, and even run over by cars on roads. It is more and more often observed that squirrels, as clear cultural followers, also climb around house facades, provided there is more than the absolutely smooth wall, and let themselves be fed on balconies and roof terraces or provide themselves with food (e.g. bird feed from birdhouses).

For sleeping and resting build squirrel nests Kobel be mentioned. These are hollow spherical buildings. They are placed in a fork of a branch or at the base of a branch, usually at heights over six meters. The diameter of the nest is about 30–50 cm, while the inside diameter is 15–20 cm. The Kobel is made of twigs, needles and leaves, inside it is padded with moss, leaves and grass. It's almost waterproof; Due to the thick walls, it offers good thermal insulation in winter. The goblins have at least two loopholes, one of which is always pointing downwards, because, unlike birds, squirrels enter their homes from below.

Building a Kobel takes about three to five days. As it is quite common that the animals have to move due to parasite infestation or disturbances, they build two to eight nests and always use them at the same time. A distinction is made between sleeping quarters for the night and shady cobbles for rest periods during the day. Abandoned caves are also used by woodpeckers , as are abandoned bird nests as a foundation for the goblin.

The squirrel is active all year round, it does not really hibernate . However, in severe winters it can show decreased activity when it does not leave the nest ( hibernation ). In very warm summers, they take a long nap in their kobeln. On hot days, they only roam very early in the morning or in the evening to get food.

Spatial organization

The home range of a squirrel varies depending on the area. On islands there are animals with action areas of less than one hectare , while in the Bavarian Forest these can be up to 47 hectares in size.

Males have larger action spaces than females. In England the males are 23–40 ha and the females 14–26 ha. The areas of activity of different individuals overlap each other. When females have young they reduce the size of their action space. Within this area, paths and locations are marked with urine and secretions from the kin glands.

Social behavior

Squirrels are mostly solitary animals . Only during the mating season do the males pursue the females within the treetops. However, they occasionally live in company outside of the breeding season; then several animals use the same goblin. The larger and older animals dominate within a group. Males are not necessarily dominant over larger and older females , but they do dominate females of the same size and age.

nutrition

A squirrel in the Berlin rose garden eats food that has been laid out

Squirrels are omnivores . The food of the animals varies depending on the season. It consists primarily of berries, nuts and other fruits and seeds. Buds, bark, tree sap, flowers, lichens, grains, mushrooms, fruit and invertebrates such as worms are also eaten. Bird eggs and young birds as well as insects, larvae and snails are also part of the food spectrum. Typically the food is held in the front paws when eating.

Squirrels consume the seeds of up to 100 spruce cones a day; an average of 80–100 g per day. When it comes to peeling spruce cones, squirrels differ from other rodents in that they simply tear off the scales of the cones with their great physical strength. In contrast, mice, for example, have to bite off the scales in order to get to the nutritious seeds. Squirrels open hazelnuts and walnuts within a few seconds. With their lower incisors they first gnaw a hole in the nut with scraping movements. If the hole is big enough, insert the lower incisors like a lever and blast out a piece of the shell. This is a learned behavior; it is not innate. Squirrels need additional ingested water.

  • Squirrel while eating a nut

  • Gnawed hazelnut

  • Gnawed pine cones

  • Squirrel garbage heap

  • Food box for squirrels, as a nutritional supplement in winter months

Squirrels build supplies in the fall for the winter. For this it is important that they find enough food to fill the stores. This does not always succeed; many of the animals may starve to death in severe winters. They either bury the food in the ground, often near tree roots, or stow it in cracks in bark or forks of branches for winter storage . They do not store any supplies in the Kobel. It is always stored in the ground in the same way: dig a hole, put food in it, scratch it, press the earth down, poke it with the nose.

In winter, the supplies are often the only source of food. If the buried supplies are forgotten, the seeds will begin to germinate in spring. This is why the squirrels are said to play an important role in the regeneration and rejuvenation of the forest. The sense of smell is very important for finding the food you have collected in autumn. Even if squirrels memorize some of their buried supplies, they are not able to memorize all of the hiding spots.

Tame squirrel

Burying supplies is a behavior that is particularly found in the populations of European deciduous and mixed forests. This behavior is mostly absent in boreal coniferous forests, as the cones , which are always available, can serve as winter food.

In some places it happens as a result of habituation that free-living squirrels eat the food offered directly from the hand of people, for example on the so-called Squirrel Path in Arosa . In Leipzig's Clara-Zetkin-Park , squirrels unafraid to help themselves from the pockets of people sitting on park benches. You can also feed the animals by hand in the park of the Pillnitz Castle near Dresden .

Squirrels eat mushrooms that are poisonous to humans.

Reproduction and development

pairing

The first approaches can be observed from the end of January, in severe winters from February. The males are attracted by vaginal secretions given off by the females in heat. Wild car chases occur during the advances. If the females are not yet ready to mate, fighting will ensue.

Once the female is ready to mate, running away becomes a game. Before mating, the female releases some urine. However, in some cases it can take days for mating to actually occur. When the time comes, the male clasps the loins of the female and mates from behind with the tail raised.

In most years there are two mating seasons , one in the late winter with litter in March or April, another in late spring with litter between May and August. If there are not enough food resources available at the beginning of the year, the first mating season can be omitted. If several males meet one female, aggressive behavior with screaming and biting can occur. Squirrels are polygynous - the males soon leave the female and look for new partners, they have nothing to do with rearing the young. If a male stays near the female until the cubs are born, it will now be bitter by the female at the latest. The male does not defend himself even if it is significantly stronger than the female ( bite inhibition ); the male then clears the field without a fight.

Rearing boys

Mother suckling three cubs
Squirrel cub
Squirrel, several weeks old

After a gestation period of 38 days, one to six young are born in the Kobel. At birth they are naked, deaf and blind ( nestling ) and weigh about 8.5 g. The body length is about 6 cm, the tail length up to 3 cm.

The young squirrels are completely covered by the first fluff after three weeks; at the same time the first teeth erupt. The young open their eyes after 30–32 days. Between the 37th and 41st days, the upper incisors break through the jaw. After six weeks they leave the nest for the first time, after eight to ten weeks they are no longer suckled and look for food independently. In the event of danger, the mothers react very quickly and carry their young in their mouths into an alternative peg.

The young remain near the maternal nest for a few more months. Squirrels become sexually mature after eleven months, but usually they do not raise young themselves until after two years. About 80 percent of the young do not survive the first year.

If a squirrel survives the first six months, an average life expectancy of three years remains . Squirrels rarely live to be seven, and in captivity they can be up to ten years old.

Predators and parasites

The pine marten is one of the squirrels' natural predators . He climbs almost as skillfully as the squirrel. While the squirrel has an advantage during the day due to its lower weight, the nocturnal pine marten likes to surprise the squirrel while sleeping. Other enemies are the wild cat , eagle owl , hawk and buzzard . Squirrels can often escape birds of prey by running around the tree trunk in circular motions. In extreme distress, the squirrel can drop to the ground from a great height without injuring itself. Young squirrels often fall prey to weasels in the Kobeln . In parks and gardens, the house cat is the squirrel's greatest enemy.

Many ectoparasites affect squirrels . The most important are the squirrel flea ( Monopsyllus sciurorum ) and the squirrel louse ( Neohaematopinus sciuri ).

In studies of squirrels in Great Britain, leprosy pathogens were detected, some of which also led to fatal diseases. According to the research of the working group, the detected bacteria Mycobacterium leprae are likely to be a strain that stayed with the squirrels and developed after an epidemic among humans. In addition to these, Mycobacterium lepromatosis was also detected as a second species .

Systematics

The Eurasian squirrel is classified as an independent species within the genus of squirrels ( Sciurus ), which today consists of a total of 28 species. The first scientific description comes from Carl von Linné , who described the species in 1758 in the 10th edition of his Systema naturae as one of the first species of squirrel and assigned it to the genus Sciurus, which he first described, as one of six rodent genera . In addition to the Eurasian squirrel, this also contained the American fox squirrels S. niger and S. cinereus , the European flying squirrel ( S. volans , today Pteromys volans ), the atlas squirrel ( S. getulus , today Atlantoxerus getulus ), the striped chipmunk ( S. striatus , today Tamias striatus ) as well as the species Sciurus flavus, which cannot be assigned .

Variations in coat color and morphology have led to the description of more than 40 subspecies of the squirrel. In Europe, for example, the color changes from south to north and northeast into a purer gray. In some areas, reddish and blackish types occur simultaneously. Seen from the Urals, the fur becomes flatter and lighter towards the west, the color is reddish to dark red in Western and Central Europe. To the east the fur becomes fuller and darker, it is darkest in Eastern Siberia. The taxonomic status of some subspecies is uncertain, and the number of recognized subspecies varies from author to author. The following system with 23 subspecies and the assignment of some synonyms follows Thorington and Hoffmann (2005). The information on the distribution is based on Sidorowicz (1971), Wiltafsky (1978), Gromow and Jerbajewa (1995) and Hoffmann and Smith (2008).

Status, threat and protection

The gray squirrel ( Sciurus carolinensis ) is gradually displacing the European red squirrel in the British Isles

General status

The IUCN ( International Union for Conservation of Nature ) classifies the squirrel as Least Concern due to its very large distribution area and large populations . Globally, there is no threat to stocks, although regional declines due to habitat loss and fragmentation of the available habitats occur.

In Mongolia in particular , heavy hunting as a fur animal and the fur trade pose a potential risk to squirrel populations.

In Germany, according to the Federal Species Protection Ordinance, as a native species , the squirrel is one of the “ specially protected species ”. The animals are therefore not allowed to be hunted, caught, killed or kept privately. Likewise, pebbles must not be removed or emptied.

Competition from gray squirrels

The North American gray squirrel , naturalized as a neozoon in Great Britain, Ireland and Italy , leads to a dramatic decline in the number of European squirrels in regions with the same occurrence due to competition. The gray squirrel is more successful than the native squirrel because it is more likely to find the food supplies buried in the autumn and also uses the supplies of the native squirrel. It is feared that an advance of the gray squirrels on the continent could push the squirrel back further and the gray squirrels could colonize large parts of the distribution area of ​​the squirrels. However, the superiority of the gray squirrels only applies to deciduous and mixed forest habitats; in coniferous forests, on the other hand, the squirrels can continue to assert themselves against their North American competitors.

In addition, gray squirrel not by infection with the Parapoxvirus croissants at Para smallpox ill and that they the virus as reservoir hosts transmitted to the squirrel, for this viral infection is often fatal. Studies in the UK found that more than 60 percent of gray squirrels are infected with the virus and that displacement of the squirrel in areas where the virus has been detected is about 20 times faster than in areas where the virus has not been detected. The virus has not yet been detected in Italy.

According to an Irish study, a sufficient population of pine marten can prevent the European red squirrels from being displaced by the gray squirrel. Scientists suspect that the European red squirrels are comparatively safer from the pine marten because they are more nimble than the gray squirrels and spend less time on the ground to eat.

Squirrel as a neozoon

Especially in Japan, where the squirrel is not native, it is regularly introduced as a pet. Due to its uncontrolled distribution, it represents a potential risk for the populations of the Japanese squirrel ( Sciurus lis ), to which it is very closely related.

Squirrel in culture

Ratatöskr on the world ash Yggdrasil. From a 17th century Icelandic manuscript.

Their Greek name σκιοῦρος skiuros ("shadow tail ") comes from the view that was widespread in ancient times that squirrels could give themselves shade with their huge tails .

In Norse mythology , the squirrel Ratatöskr can be found walking up and down the Yggdrasil World Ash .

Squirrel skins have been used to make clothes since ancient times ; the skins are known as feh . The winter coats of the Siberian subspecies of the European squirrel with the blue-gray back and the white belly side were considered to be particularly valuable. The processed fur is represented as a symbolic status mark as a heraldic feh in coats of arms.

Finds of remains in the Neolithic pile dwellings in Switzerland show that squirrels were also eaten in the past .

The city of Eckernförde and the communities Westensee and Emkendorf u. a. show the animal on the coat of arms , see squirrel ( heraldic animal)

literature

  • Richard W. Thorington Jr. , John L. Koprowski, Michael A. Steele: Squirrels of the World. Johns Hopkins University Press, Baltimore MD 2012, ISBN 978-1-4214-0469-1 , pp. 73-76 .
  • Igor Michailowitsch Gromow and Margarita Alexandrowna Jerbajewa: The mammals of Russia and neighboring areas. Rabbits and rodents . Russian Academy of Sciences, Saint Petersburg 1995 ( full text ( memento from March 15, 2005 in the Internet Archive ) - 520 pages, original Russian title: Млекопитающие фауны России и сопредельных террильных терриызуныг).
  • Peter WW Lurz, John Gurnell and Louise Magris: Sciurus vulgaris . In: Mammalian Species . No. 769 , 2005, ISSN  1545-1410 , pp. 1–10 ( full text as PDF ).
  • Sibylle Münch: Squirrel. Sciurus vulgaris Linnaeus, 1758 . In: Monika Braun and Fritz Dieterlen (eds.): The mammals of Baden-Württemberg. Volume 2 . Eugen Ulmer, Stuttgart 2005, ISBN 3-8001-4246-5 , pp. 153-166 .
  • J. Sidorowicz: Problems of subspecific taxonomy of squirrel ( Sciurus vulgaris L.) in Palaearctic . In: Zoologischer Anzeiger . tape 187 , 1971, ISSN  0044-5231 , pp. 123-142 .
  • Herbert Wiltafsky: Sciurus vulgaris Linnaeus, 1758 - squirrel . In: Jochen Niethammer and Franz Krapp (eds.): Handbook of Mammals in Europe. Volume 1. Rodents I . Akademische Verlagsgesellschaft, Wiesbaden 1978, ISBN 3-400-00458-8 , p. 86-105 .
  • Josef H. Reichholf and Johann Brandstetter (illustrator): The life of the squirrel. Munich: Hanser, 2019, ISBN 978-3-446-26407-6 .

Web links

Commons : Sciurus vulgaris  - album with pictures, videos and audio files

Individual evidence

  1. ↑ Etymological dictionary of the German language . 18th ed., Edit. by Walther Mitzka. Walter de Gruyter, Berlin 1960, p. 154 f .; Schweizerisches Idiotikon , Volume I, Sp. 73.
  2. ↑ a b c d e f g h i j k Wolfgang violence: The squirrel . A. Ziemsen Verlag, 1956, ISBN 3-89432-164-4 .
  3. ↑ a b c d e Lurz and coworkers, 2005 ("Form and Function" p. 3).
  4. ↑ Lurz et al., 2005 (“Diagnosis” pp. 1–2).
  5. ↑ a b c d Wiltafsky, 1978 ("Description", pp. 86–87).
  6. ↑ a b Gromow and Jerbajewa: Obyknowennaja belka - Sciurus (Sciurus) vulgaris . 1995, archived from the original on March 19, 2007 ; Retrieved January 25, 2013 (Russian).
  7. ↑ Wiltafsky, 1978 ("Diagnose" p. 87).
  8. ↑ a b Gromow and Jerbajewa: Rod belki - Sciurus . 1995, archived from the original on March 20, 2007 ; Retrieved January 25, 2013 (Russian).
  9. ↑ a b Lurz et al. , 2005 (“General Characters” p. 2).
  10. ↑ a b c Wiltafsky, 1978 (“Characteristic Variations”, pp. 92–98).
  11. ↑ Münch, 2005 (“Description” pp. 153–156).
  12. ^ Jochen Niethammer and Franz Krapp (eds.): Handbook of Mammals in Europe. Volume 1. Rodents I . Akademische Verlagsgesellschaft, Wiesbaden 1978, ISBN 3-400-00458-8 (476 pages; Fig. 12).
  13. ↑ a b Heinrich Dathe, Paul Schöps: Pelztieratlas . VEB Gustav Fischer Verlag, Jena 1986, pp. 95-98.
  14. ↑ a b c d e f g h i Sciurus vulgaris in the Red List of Threatened Species of IUCN 2015-4. Posted by: S. Shar, D. Lkhagvasuren, S. Bertolino, H. Henttonen, B. Kryštufek, H. Meinig, 2002. Accessed May 19, 2016.
  15. ^ A b Franz Robiller: Animals of the night. Urania-Verlag, ISBN 3-332-00108-6 .
  16. ↑ Video clip 1 feeding on the Eichhörnli-Weg Arosa (1957)
  17. ↑ Video clip 2 feeding on the Eichhörnli-Weg Arosa (1957)
  18. ↑ The squirrel at Eifel Nature
  19. ↑ Charlotte Avanzi, Jorge del-Pozo, Andrej Benjak, Karen Stevenson, Victor R. Simpson, Philippe Busso, Joyce McLuckie, Chloé Loiseau, Colin Lawton, Janne Schoening, Darren J. Shaw, Jérémie Piton, Lucio Vera-Cabrera, Jesùs S. Velarde-Felix, Fergal McDermott, Stephen V. Gordon, Stewart T. Cole, Anna L. Meredith: Red squirrels in the British Isles are infected with leprosy bacilli. Science 354 (6313), Nov. 11, 2016; Pp. 744-747, doi : 10.1126 / science.aah3783 .
  20. ^ Carl von Linné : Systema naturae. 10th edition, 1758; Volume 1, pp. 60, 63-64 ( digitized version ).
  21. ^ Lurz and employees, 2005 ("Context and Content" p. 1).
  22. ^ Richard W. Thorington junior and Robert S. Hoffmann: Family Sciuridae . In: Don E. Wilson, DeeAnn M. Reeder (Eds.): Mammal Species of the World . A Taxonomic and Geographic Reference . 3. Edition. Johns Hopkins University Press, Baltimore 2005, ISBN 0-8018-8221-4 , pp. 754-818 ( " Sciurus vulgaris " p. 764).
  23. ↑ Sidorowicz, 1971. Quoted in: Lurz and employees, 2005 (“Context and Content” p. 1).
  24. ↑ Wiltafsky, 1978 (“Spread”, pp. 90–92, Fig. 22).
  25. ^ Robert S. Hoffmann, Andrew T. Smith: Family Sciuridae . In: Andrew T. Smith, Xie Yan (Eds.): A Guide to the Mammals of China . Princeton University Press, Princeton / Oxford 2008, ISBN 978-0-691-09984-2 , pp. 172–196 (“Eurasian Red Squirrel” p. 181).
  26. ↑ "Fight" of the squirrels - gray squirrel ousts squirrels. Archived from the original on February 6, 2012 ; accessed on January 31, 2017 .
  27. ^ FAZ Tierwelt
  28. ↑ Red squirrel finds pine marten a fearsome ally in its fight for survival. The Guardian, February 22, 2013, accessed November 21, 2015 .
  29. ^ Henry George Liddell, Henry Stuart Jones, Robert Scott: A Greek-English lexicon, A new ed. (9th), rev. and augm. throughout / by Henry Stuart Jones, Oxford, Clarendon Pr. 1951.
  30. ↑ a b c Bernhard Grzimek (Ed.): Grzimeks Tierleben , Volume 11: Mammals 2 . dtv-Verlag, 1979, p. 250 ff.
  31. ↑ the Siberian squirrel known in the fur trade as “Feh” “Sciurus vulgaris exalbidus” (synonyms: S. v. Argenteus, S. v. Kalbinensis) Entry on www.zoodirektoren.de; accessed on November 12, 2017