Grey squirrels introduced from North America have driven red squirrel decline across Britain through competition and disease. Management programs raise complex welfare questions about killing invasive species.
Lethal trapping of grey squirrels raises welfare questions about killing abundant sentient mammals to protect a declining species. The welfare of individual grey squirrels killed conflicts with population-level conservation of red squirrels. There is no comfortable answer — but developing humane alternatives like immunocontraception that avoid killing while managing populations represents the most welfare-positive path.