A tale of two squirrels

 
 

A deadly virus has reached our shores and is set to devastate our already ailing red squirrel population. Alison Lee writes about the dangers posed and the efforts being made to save the creatures.

Cast your mind back to your primary school days and you will probably remember learning about Ireland’s wildlife. You might even remember the term ‘Iora rua’, or ‘red squirrel’. This shy tree-dwelling mammal can still be found in forests across the country, but this may not be the situation for much longer.

Since the introduction of the grey squirrel to Longford in 1911, red squirrels have grown scarcer and their distribution has shrunk dramatically; so much so that the National Parks and Wildlife Service has had to take measures to protect it. Ireland isn’t the only country where this animal is in danger; the red squirrel has become extinct in England and Wales due to the introduction of the grey squirrel in 1876. However, another factor helped along the disappearance of red squirrels in the UK: the lethal squirrel pox virus (SQPV). It was long believed that Ireland was free of this disease – that is, until now.

This January, the first Irish case of SQPV was confirmed by Prof. Sean Callanan of the UCD Veterinary Pathology Department. The squirrel was found by local resident Kevin Phelan while walking in woods in Hollywood, County Wicklow and since then two more cases of the disease have been confirmed. This development could spell doom for our native squirrels.

It is widely believed that grey squirrels fight with and kill their red counterparts, but this is not the case. They are simply bigger, breed faster, have more young per litter, and can exist at higher population densities – therefore they have displaced the red squirrel population by competition. Reds are now mostly found in inhospitable pine forests where food is too scarce for greys to thrive.

Grey squirrels are simply more adaptive – they are happy to live near humans and although they’re cute and playful, they can be extremely destructive to homes and gardens. This has resulted in them being classed as a household pest alongside rats, wasps etc. They also strip bark off trees and significantly impact upon commercial broadleaf timber production.

Grey squirrels have another means of thinning out the red squirrel population; it is believed they are carriers of the squirrel pox virus, but have evolved an immunity and thus are resistant to its potentially deadly effects. It is yet unknown how they transmit the disease to red squirrels, but scientists believe it may be passed on via secretions from scent glands that they use to mark their territories. Its effects on non-immune squirrel species are devastating.

The virus causes lesions similar to those seen in rabbits with myxomatosis – swellings, ulcers and scabs develop around the animals’ eyes, mouth, nose and paws and it is believed the squirrels simply die of dehydration, respiratory problems and starvation as they cannot forage for food or eat. The virus does not seem to affect their internal organs.

Yet there may still be hope for the red squirrel – in 2008, a UK scientist discovered a handful of animals that had developed antibodies to the disease, thus indicating that some red squirrels have the potential to become immune. When myxomatosis was introduced to the UK in the 1950s, the death rate amongst rabbits was almost one hundred per cent, but those with a natural immunity survived, bred and now the death rate has decreased to thirty-five per cent. A similar situation may occur if enough red squirrels develop an immunity to the disease and live long enough to produce immune young. The development of an SQPV vaccine could also theoretically save the red squirrel. In fact, a Scotland-based charity called Wildlife Ark Trust are currently trying to do just that, but it will take at least another year to develop an effective vaccine, and subsequently three years of trials will be required before it can be used in the wild.

So what lies ahead for our red squirrels? If the virus spreads throughout the country it is likely that they will go the same way as their counterparts in England and Wales. Although the loss of a native species would indeed be tragic, Darwin’s principle of “survival of the fittest” doesn’t take pity or make exceptions for any animals, no matter how cute or charismatic they may be.

Since humans set this tragedy in motion by introducing grey squirrels to Ireland, it is only right that we at least make an attempt to preserve one of the few Irish mammals that still survive in the wild. This will require measures such as supplementary feeding, monitoring and recording squirrel numbers, careful forest management and the humane culling of grey squirrels. Yet these measures require money and resources that Ireland is currently lacking. Therefore the future may be bleak for Iora Rua – only time will tell.

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