Two different squirrels

Although two types of squirrel species can be seen in Scotland today, this wasn't always the case. 

The red squirrel is classed as a native species to the UK.  The first evidence of the red squirrel in Britain appears at the end of the last Ice Age (10,000 years ago).  Red squirrels were once the only squirrel species in Britain and were widely distributed.    

The grey squirrel is classed as an invasive non-native species in the UK.  Grey squirrels have been introduced to the UK at various locations since the 19th Century.  They were first introduced in 1876 by the Victorians, who regarded the grey squirrel as an exotic species. 

The spread of grey squirrels is the main threat to red squirrel survival and the main reason for their catastrophic decline in Britain.  Grey squirrels compete more successfully than red squirrels for food and habitat, they are larger and more robust, and can digest seeds with high tannin content, such as acorns, more efficiently.  This means grey squirrels can access a more abundant food supply than red squirrels.  As a result, the arrival of grey squirrels in an area occupied by red squirrels tends to cause reduced red squirrel breeding and survival rates leading to a gradual decline in their numbers.  

Grey squirrels can also carry squirrelpox virus (SQPV), which causes severe clinical disease and mortality in red squirrels without causing any symptoms in the grey carriers. The presence of this disease in grey squirrels in England and Wales has caused the replacement of red squirrels by grey squirrels to happen 17 to 25 times faster than where the greys do not carry the disease.  At present SQPV in Scotland is confined to 7 main river corridors in South Scotland: the Liddel, the Esk, the Nith, the Annan, the Tweed, the Blackadder and the Whiteadder . Saving Scotland's Red Squirrels' regional branch, Red Squirrels in South Scotland , is focussing current work on containing and reversing the spread of the virus.

Read our key facts sheet to find our more about the differences between red and grey squirrels.

For more information about the reasons why grey squirrels outcompete red squirrels, go to the squirrel page on the Aberdeen University website.

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