The decline of the Red Squirrel in the British Isles
The gray squirrel is native to the United States and was introduced to parks in Britain and Ireland. They caused the local extinction.
The maps below show the ranges of Red Squirrel and Grey Squirell in 1945 and 2010 in Great Britain and Ireland.
The Grey Squirrel and the red squirrel are not directly opposing, and brutal conflict among these species is not a factor in the drop in red squirrel populations. But, the Grey Squirrel arrives to be capable of reducing the red squirrel population due to the following causes:
- Grey Squirrel transfers a disease, the squirrel parapoxvirus, that does not develop to influence their health but will frequently kill the red squirrel. In 2008, the number of red squirrels at Formby in England had decreased by 80% because of this disease, though the population is presently growing.
- Grey Squirrel can better digest acorns, while the red squirrel cannot efficiently obtain the proteins and fats in acorns.
- When the red squirrel is placed under pressure, it will not breed as frequently.
In the United Kingdom, the population has dropped to 160 thousand red squirrels or less (120 thousand are in Scotland). Outside the United Kingdom and Ireland, conflict from the Grey Squirrel has been witnessed in Italian Piedmont, where two pairs left from captivity in 1948. A notable decline in red squirrel populations in the area has been observed since 1970, and it is worried that the Grey Squirrel may extend into the rest of Europe.