Squirrels Interaction with Other Species - Decline of the Red

Since their initial introduction to the UK during the late 19th Century—with at least 32 documented releases between 1876 and 1930—the Grey squirrel has flourished, apparently at the expense of the Red. This subject is covered at greater depth in my Questions and Answers section, but the abridged story is that since about 1920, when only around 13 small populations of Greys were present in the UK, the Grey squirrel has expanded its range northwards. Some areas have seen declines in Reds that closely match the spread of the Grey, while in other parts of the country the two species have co-existed for many years.

Once persecuted as pests to forestry, Red squirrels are now one of the UK's most popular animals, taking third place in a poll of 5,000 Britons in 2016. - Credit: Marc Baldwin

It appears that loss of habitat is a factor in the decline of the Red, but there is also evidence suggesting that Reds do not generally survive well in the presence of Greys. Initially, it was thought that Greys physically excluded Reds, by fighting with them and driving them out of an area. We now know that this is not the case – Greys actually competitively exclude Reds, i.e. they monopolise food resources.

The squirrelpox virus, which can be carried by Greys but is usually fatal to Reds, also appears to be a significant factor in the Red squirrel’s decline; populations fall up to 25 times faster in areas with squirrelpox. There are several projects underway to understand the decline with a view to reversing it. Some projects have attempted to exterminate Greys from prime Red squirrel habitat, but such schemes are costly, long-term and have, with only a couple of exceptions, failed. Achieving complete elimination of the Grey squirrel from the UK seems highly unlikely at this time.

Humans imported Grey squirrels to Britain and in many cases released them into the wild. Humans have also implemented poor environmental management strategies that appear to have benefited the Grey at the expense of the Red. Ultimately, humans are primarily responsible for the Red squirrel’s decline in Britain. It seems fitting, therefore, that we are now trying to redress the balance and restore Red squirrel populations in the country (see QA for further details) and that, towards the end of 2016, Trees for Life announced an ambitious plan to establish 10 new Red squirrel populations in the northwest Highlands as part of a project funded by the People’s Trust for Endangered Species and a grant from the Heritage Lottery Fund.

Since their introduction by the Victorians, Grey squirrels (Sciurus carolinensis) have readily adapted to city parks and gardens, much more so than Reds have, and may be the only wildlife some city-dwellers ever interact with. - Credit: Marc Baldwin

In conclusion, since the end of the last ice age, when a small tree-dwelling rodent crossed that which is now the English Channel from mainland Europe to invade our birch and pine forests, the squirrel has been almost monarchic to our nation; hunted for food and fur while also capturing our hearts and imaginations. As the ice retreated northwards, the forests and the squirrels dwelling in them followed, such that the Red squirrel was commonplace across the UK.

During the 1800s, Victorians released several Greys that they imported from America and, unfortunately, various management practices, interspecific competition elements between the two species and disease lead to a rapid and widespread decline in the Red squirrel. To the contrary, the Grey squirrel has thrived in the UK and is now the commonplace sciurid throughout most of the British Isles. Part of the Grey’s success is undoubtedly a result of how easily it adapts to our urban sprawl, feeding on our leftovers and being perfectly at home in our towns, cities and back gardens.

Hopefully, through the conservation partnerships and legal measures currently in force, combined with the considerable effort being directed to Red squirrel preservation and reinstatement, we will see an increase in the squirrel species that has been an enigmatic character on the British landscape for almost 10,000 years.