Red squirrel populations have been devastated by competition from grey squirrels and squirrelpox virus. Conservation efforts focus on disease-free refugia.
Squirrelpox causes severe welfare harm to infected red squirrels, causing skin lesions, eye discharge, and death within weeks. Grey squirrel control to protect red squirrel refugia raises ethical questions about killing one species to protect another. Vaccination, if successful, would remove the need for lethal control.