The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia. The red squirrel is an arboreal, omnivorous rodent.In Great Britain, Italy and Ireland, numbers have decreased drastically in recent years, a decline associated with the introduction of the eastern grey squirrel from North America,although habitat loss is also a factor.he red squirrel has a typical head-and-body length of 19 to 23 cm a tail length of 15 to 20 cm and a mass of 250 to 340 g . It is not sexually dimorphic, as males and females are the same size. The red squirrel is somewhat smaller than the eastern grey squirrel which has a head-and-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 different coat colours co-exist within populations, much like hair colour in some human populations. 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 between August and November. A lighter, redder overall coat colour, along with the ear-tufts and smaller size, distinguish the Eurasian red squirrel from the American eastern grey squirrel.