Pine marten recovery has been shown to suppress grey squirrel populations through predation, facilitating red squirrel recovery in a natural ecological relationship with welfare implications for all species involved.
The pine marten and squirrel welfare story illustrates the complexity of welfare assessment in multi-species ecological systems. Pine marten predation causes death and suffering to individual grey squirrels. At the population level, this predation reduces the competitive exclusion of red squirrels that has driven their near-extinction from much of Britain. Grey squirrel culling programs cause welfare harm to many more individuals than pine marten predation. The ecological welfare calculus favors pine marten recovery as both more humane and more effective for red squirrel welfare than intensive culling. This case demonstrates that ecosystem-level thinking sometimes reveals welfare-positive approaches that individual-focused assessment misses.