The native red squirrel (Sciurus vulgaris) has been displaced from 97% of its former UK range by the introduced North American grey squirrel (Sciurus carolinensis). Conservation management involves lethal grey squirrel control — creating a welfare dilemma between two squirrel species.
Grey squirrels caught in live traps await killing by the trapper — typically through dispatch within 24 hours, though trap-checking intervals vary. Cage traps cause acute stress from confinement. Red squirrels infected with squirrelpox develop facial lesions, eye swelling, and ulcerations that cause prolonged suffering before death — a welfare harm attributable to introduced grey squirrels carrying the virus asymptomatically. Conservation welfare requires weighing the welfare cost of lethal grey squirrel control against the welfare harm caused by squirrelpox in red squirrel populations. Immunocontraception, if successfully developed, would eliminate lethal control welfare costs.