How to distinguish red and grey squirrels?

• Colour - but is it so simple?
  
• Size and weight: obvious differences
  
• Less obvious differences
  
• Bibliography
  

Colour - but is it so simple?

The names - red and grey squirrel, although true in most cases may be confusing in certain parts of the year. The red squirrel doesn't always appear red and grey is not always grey. In fact, the coat changes during the year in both species and seasonal differences occur.
In summer the red is easily distinguished. Its coat is orange-red and is often thought to be 'typical'. In winter the red squirrel has brownish-grey fur with white underpants, somehow resembling the grey. In some British subspecies the coat bleaches with time becoming slightly paler. At times other colour phenomenons are observed: white tails in red squirrels or even albino types. Melanic, black squirrels are also reported. Both of the extreme colour types are present in the grey squirrel as well. The grey squirrel doesn't seem to appear grey when separate hair are examined. Those can be brown, black or white and rarely single grey hairs are found. In winter, the grey squirrel displays silver-grey coat, but some shaded of yellow brown and black can also be observed. In summer the grey appears to be more brownish than in the cold months. Two moults are observed in both species and sometimes cause confusion in saying which species is which.

Size and weight: obvious differences

Red squirrels are much smaller and lighter than the grey. Depending on the data you look into the differences are smaller of greater magnitude, but are always present. Data from Laider are: 219mm in body length 182mm in tail length and average weight of 300g in red squirrel. The grey squirrel on the other hand was found to be on average: 457mm in body length and 510-567g in weight. Thus, when both species of the same age are seen together and one squirrel is twice the size of the other we can assume that its the grey.

Less obvious differences

• Ear tufts are quite a distiguishable feature of the red squirrel, reaching as much as 35mm length. In the grey squirrel they are present in winter. In summer the grey squirrel lacks this feature, still ear tufts of the red squirrel may be reduced in winter.
  
• Red squirrel's tail appears to be shorter and more bushy in comparison to the grey's.
  
• The red's its face tends to be more pointed.
  
• Red squirrel is an arboreal species and therefore moves with more grace than the grey, which tends to be more swift on the ground.
  

Bibliography

• Shorten, M. (1954). Squirrels.1st ed. Collins: St. James’s Place London.
  
• Laider, K. (1980). Squirrels in Britain. 1st ed. David & Charles: Newton Abbot London North Pomfeet (Vt).
  
• ARKive. Images of live on earth. (2003) [Online] Available from: http://www.arkive.org [Accessed on: 4 December 2008]
  
• The Friends of the Anglesey Red Squirrels. (2008) UK Red & Grey Squirrel Pictures. [Online] Available from: http://www.redsquirrels.info/squirrelpics.html [Accessed on: 4 December 2008]