Red squirrels are at risk of extinction in England and Wales, partly due to squirrelpox virus carried asymptomatically by grey squirrels and lethal to red squirrels. The disease causes severe welfare impacts and is a barrier to red squirrel range expansion.
Red squirrels dying of squirrelpox experience progressive skin lesions, eye swelling, respiratory distress, and behavioural deterioration over 1-2 weeks. The suffering is prolonged and painful. The disease creates a welfare dilemma in which the control of grey squirrels (through lethal methods) is justified by the prevention of greater welfare harm to red squirrels. The ethics of lethal grey squirrel control are complex but the welfare case for red squirrel protection is compelling.