Earlier this year on May 11th came the news that many involved in conservation had feared for a long time: a red squirrel infected with parapoxvirus had been found in Scotland. The finding of this infected animal in the Lockerbie area of the Scottish borders represented a significant defeat for conservation groups who had been, until then successfully, working to prevent the spread of the disease into Scotland and to prevent its movement between the grey and red squirrel populations.

The population of British red squirrels has been retreating northwards for many years as the stronger, more adaptable and disease carrying grey squirrel has spread relentlessly northwards since its initial introduction in southern England.

  

An invasive alien species – big, robust and perfectly adapted to life in Britain. Image by Gotigersjf. Some rights reserved.

Aside from a few remnant populations in England and Wales, it is now estimated that over 75% of the remaining red squirrels in the UK (approximately 121,000) are in Scotland, an area where the grey squirrel has only recently begun to invade.

With the confirmation that the parapoxvirus has now arrived in both the grey and red Scottish squirrel populations, there are many who will now feel that the extinction of the red squirrel is now an ever more likely outcome.

The decline of the red squirrel is not only due to the spread of the grey, but red squirrel populations made vulnerable by the destruction of their habitat are poorly adapted to compete with their more robust and adaptable north American cousins.

There are habitats, such as coniferous woodlands, where the reds can hold their own against the greys and there are some who believe that in appropriately managed woodland they could live together. Unfortunately, grey squirrels also have another huge advantage over reds and that is that they are not significantly impaired by infection with squirrel parapoxvirus, while the British red squirrel is. This means that, in habitats where red and greys co-exist and where there is also parapoxvirus, the reds are at such a huge competitive disadvantage that, even if they survive the disease, they cannot possibly persist for long.

The question of what should be done is an extremely controversial one. There are many who believe that culling of greys is the answer and millions of pounds are being spent to prevent the spread of grey squirrels into areas where reds remain using rodenticides and traps of numerous types. The problem with this approach is that they can impact on non-target species and there is significant public opinion in support of the grey squirrel, which for many is a nice addition to our urban and rural greenspaces.

As a result, there are many who believe that non-lethal approaches should be adopted. These generally involve interventions that improve the red squirrel’s ability to compete with the grey and range from the introduction of selective food hoppers, from which only the reds can feed, to developing vaccines against the parapoxvirus.

Whatever the approach selected, it now seems that we are fighting a losing battle. There are insufficient funds and manpower available to stem the tide of grey squirrels advancing across the country and it is unclear whether a vaccination strategy can be developed in time.

Are we then resigned to losing the red squirrel? Perhaps we should not worry – our squirrel biodiversity will still read as one species after all, and surely we could just do what they did for red kites and introduce some red squirrels from Europe, where there are still loads of them?

 

A European red squirrel. Could these animals be used to bolster the British population? Image by Ray Eye, Germany. Some rights reserved.

Unfortunately it’s not that simple. Genetic studies have now shown that the British red squirrel is taxonomically different from the European races and so, while a reintroduction could give us back red squirrels, which would be something, we would still have lost a unique and important part of our natural heritage forever.

For more information about grey squirrels read the new CI-UK Article, ‘The Grey Squirrel in Britain: A Major Threat to Biodiversity’.

Read the original story about the Scottish red squirrel infected with parapoxvirus at the BBC News website.