The red squirrel (Sciurus vulgaris) is Britain's only native squirrel species and a much-loved conservation icon. Displaced from most of England and Wales by the introduced grey squirrel (Sciurus carolinensis), red squirrels now persist mainly in Scotland, with small refugia populations in Northumberland, the Lake District, Isle of Wight, and Anglesey.
Red squirrels are diurnal (day-active), arboreal rodents that inhabit mixed and coniferous woodland, feeding primarily on seeds, nuts, fungi, and tree buds. They cache food in autumn for winter use, relying on memory and scent to relocate caches. Unlike grey squirrels, red squirrels cannot efficiently digest the tannins in mature acorns and are therefore less competitive in broadleaved woodland. Scots pine, Sitka spruce, and Norway spruce woodlands provide optimal habitat where greys are disadvantaged.
Grey squirrels outcompete red squirrels for food, territory, and resources, and carry squirrelpox virus (SQPV) which is lethal to red squirrels (causing death within 2 weeks of infection) but to which grey squirrels have immunity. SQPV transmission from grey squirrels has caused catastrophic red squirrel population collapses in former refugia. The combination of resource competition and disease means that red squirrel survival in mixed woodland with grey squirrels is virtually impossible.
Red squirrel conservation requires maintaining populations in grey squirrel-free or low grey-density areas. Strategies include: grey squirrel management (trapping, shooting) in buffer zones around red squirrel refugia, provision of supplementary food to support red squirrel populations, vaccination of red squirrels against squirrelpox (available and used in UK refugia), habitat management to maintain coniferous woodland, and potential future use of immunocontraception in grey squirrel populations.
Conservation interventions for red squirrels include: trapping for health monitoring (using appropriate traps checked regularly to prevent suffering), blood sampling for disease surveillance, vaccinating against squirrelpox (live attenuated oral vaccine delivered in hazelnut paste-baited feeders—minimising capture stress), fitting GPS tags for movement studies, and treating mange or other conditions in wild individuals. All interventions require appropriate permits and welfare protocols.
Grey squirrel management for red squirrel conservation raises genuine welfare dilemmas—killing grey squirrels (sentient, native to North America, introduced to the UK without fault) to protect red squirrels involves trading welfare costs of one species against conservation benefits for another. Humaneness of lethal control methods (trapping and shooting), identification of grey squirrels before lethal control, and proportionality of management to conservation need are important ethical considerations.
Pine marten recovery in Scotland and Ireland has been associated with grey squirrel population declines and red squirrel comeback in the same areas. Grey squirrels spend more time on the ground and are less adept at escaping arboreal predators, while red squirrels may be better able to avoid pine martens by remaining in the canopy. This natural suppression mechanism offers a welfare-friendlier alternative to lethal grey squirrel management in areas where pine martens are recovering.