Controlling the grey squirrel population

The red squirrel, Sciurus vulgaris, are native to Ireland. They are under threat of local extinction largely due to the presence of the grey squirrel, Sciurus carolinensis, an invasive alien species which was introduced just over 100 years ago in 1911 to county Longford from England.

Red squirrel by tree The problem

The greys had been established in Great Britain from their native North America several years before.  Only 12 animals were shipped from England to Ireland as a wedding present – they subsequently escaped.  By 1960s they were spreading across the Northern Irish border and have since colonised much of the suitable countryside.

Fact: Genetic research has determined that all the grey squirrels in Ireland are related back the original 12 animals brought to the island in 1911.  This suggests that the invasive species problem has been caused by a single incident.

When the grey squirrel arrives in a red squirrel area, the red squirrel population usually disappears within 15 years. The grey squirrel outcompetes the red for food, space and carries a disease, called the squirrel pox virus. This disease kills the red squirrel but has no known lasting effect on the greys. In circumstances where the presence of squirrel pox is confirmed, the extinction rate of red squirrels can be 20 to 25 times faster than that in pox free areas.

Adapting to habitat change

The red squirrels have also suffered because of the continued loss of quality habitat across the island, isolating populations and further reducing the survival chances for this charismatic little mammal. 

Northern Ireland has a very small percentage of tree cover compared to other European countries, which limits the available habitat for Red Squirrels. Additionally red squirrels are already under pressure from habitat loss across Northern Ireland. 

Grey squirrel on ground The primary issue is the spread of the grey squirrel because the greys can thrive in conditions that would be difficult for red squirrels. So, where habitat is lost to development or agriculture the greys can continue to live in parks, gardens and hedgerows.

Reds struggle in these lesser habitats and are generally restricted to commercial forestry plantations. Greys can eat seeds and nuts that are not ripe enough for the reds to digest so they get the food first.  As the grey squirrel lives at considerably higher densities they also cause considerable damage to nesting birds and trees.  In the urban environment grey squirrels raid bird feeders, bins and have been known to damage roofs.

Fact: To help our iconic native animals will must reduce the number of grey squirrels they have contact with. 

The solution

The only sustainable way to conserve the Red Squirrel in the UK and Ireland is to remove the grey squirrel from the habitats suitable for red squirrels.

Ultimately the ideal way to secure the red squirrels future is the complete eradication of the grey from the islands, however this is currently an unachievable target given the available resources and would be practically very difficult.  

Several scientific solutions are being investigated currently but none of these are ready to be field trialled.  

How can I help?

If you have grey squirrels entering your garden do not feed them.  Make sure your bird feeders are 'squirrel proofed'.

Red squirrel feeding If you are lucky enough to have red squirrels in your garden and they are feeding on bird feeders, you should disinfect these feeders regularly by firstly using a household detergent and clean away any dirt, followed by a soak in a broad spectrum disinfectant or a 5-10% bleach solution for at least 15 minutes and then rinse in cold water. This is good practice even if you don’t have squirrels as diseases can spread between birds and other wildlife at feeding stations.  

The Northern Ireland Squirrel Forum (NISF) have produced detailed guidance on trap and feeder hygiene and this available to view and download here 

Encourage grey squirrel management within parks and open spaces. These places offer breeding sites for the greys which then spread out to surrounding areas. The grey squirrel can live in high densities, causing significant damage to trees and plants. If you are land owner or farmer control any grey squirrels on your property.

If you are land owner or farmer control any grey squirrels on your property.

Particularly important if you have both grey and red squirrels visiting your site.  We encourage grey control on all properties, but appreciate this is not everyone’s ‘cup of tea’.

Important: If you trap a grey squirrel you must not release it this is illegal. Releasing or moving it to another area will potentially put our red squirrels in danger.  The grey squirrel must be humanely dispatched.

If you have a very large garden or farmland which has tree cover and there are grey squirrels living there you should consider some control measures. If you would like assistance with grey squirrel control our NISF partners BASC NI and SAC NI will happily direct you toward their local members who will have appropriate training and insurance to allow airgun dispatch of squirrels providing it is safe to do so. Or if you are adjacent to one of our red squirrel groups their members may be able to assist you.

Or contact the NIEA for further advice:

The NISF has produced detailed guidelines on how grey squirrel control should be carried out to adhere to animal welfare legislation and to keep the operator and the public safe. These guidelines are available to download here.


Volunteer with your local Red Squirrel Group or start a new one if there are none close to you, we can help. Further information on the work and locations of the Red Squirrel Groups in Northern Ireland is available at the link below:

Sightings – your records are important!

You can record sightings of red and grey squirrels in Northern Ireland online on the Centre for Environmental Data and Recording (CEDaR) website. 

You can also record sightings of pine marten in Northern Ireland.

Distribution maps of red / grey squirrels and pine marten

The recorded distribution of red / grey squirrels and pine marten in Northern Ireland between 2007-17. From these maps you can see there are key areas that we must reduce the contact between reds and greys. 

Red Squirrel distribution map 2007-2017
Red Squirrel distribution map 2007-2017

Grey squirrels distribution map 2007-2017
Grey squirrels distribution map 2007-2017

Pine marten distribution map 2007-2017
Pine marten distribution map 2007-2017

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