Grey squirrel

Sciurus carolinensis


Photo credit: ©GBNNSS
Sciurus carolinensis  
  • The species preferred habitat is mature woodlands with a diverse understory however; in Ireland the species is common in agricultural lands, planted forests, scrub or shrublands, and urban areas.

Widely Spread Species:
  • Under Article 19 of Invasive Alien Species Regulation (1143/2014) Grey squirrel has been identified as a Widely Spread Species in Northern Ireland and as such, management measures have been put in place to minimise its impacts.

  • The grey squirrel is a larger tree squirrel than the native red squirrel. It has a distinctive long bushy tail and characteristic short front legs.
  • Colouration is known to vary with some specimens displaying ‘chestnut’ markings on paws, hips and face which can lead to misidentification. In winter the species displays a thick winter grey/silver coat on the upper side of the body with a white under side.
  • The total length of these squirrels ranges from 430-500 mm, tail length ranges from tail 210-240 mm, and generally is 400-710 g. in weight.

Download N.I.E.A. ID guide

Origin and Distribution:
  • Originated from North America but was introduced to Europe to ‘improve’ diversity of estates in the late 19th century and early 20th century.

  • Grey squirrel is considered the main threat to the endangered and protected red squirrel
  • They out compete the red for space and food and are also a known vector for the Squirrel pox virus which can be fatal to red squirrels
  • Grey squirrels also cause economic loss to forestry plantations by stripping the bark of trees which can lead to tree die off

How did it get here?
  • Deliberate release

Is it found in Ireland or Northern Ireland?
  • Grey squirrels are found in most areas of Northern Ireland. 
  • More distribution information can be seen at the NBN Atlas NI.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Methods for prevention:
  • This species is very widespread across the island of Ireland, and total eradication is unlikely
  • Grey squirrel control is being concentrated in areas where there is the greatest chance that reds can be re-established
  • Focus remains on humanely controlling the species to prevent the spread of damage to habitats and other wildlife
  • Report all sightings to CEDaR

Current Legislative Position (Listed on 03 August 2016)
  • This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.

Grey squirrel research:

The dynamics of pine marten predation on red and grey squirrels

Implications of squirrelpox virus for successful red squirrel translocations within mainland UK

Declining invasive grey squirrel populations may persist in refugia as native predator recovery reverses squirrel species replacement

Reinstating trophic cascades as an applied conservation tool to protect forest ecosystems from invasive grey squirrels (Sciurus carolinensis)

The management of the introduced grey squirrel seen through the eyes of the media

The drivers of squirrelpox virus dynamics in its grey squirrel reservoir host

The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations

For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email:

Species Related Files:

Invasive Species Northern Ireland

Invasive Species Northern Ireland