The recovery of pine martens in parts of the UK has complex welfare implications for multiple species, particularly native red squirrels and invasive grey squirrels.
Pine marten recovery creates a complex welfare picture across multiple species. Individual pine martens released in reintroduction programs face the welfare challenges of translocation - stress of capture, transport, and establishing territory in unfamiliar habitat. Grey squirrels that encounter pine martens experience predation pressure from a relatively novel predator. Red squirrels in areas of pine marten recovery appear to benefit from competitive release as grey squirrel numbers decline. The prey populations affected by marten predation experience individual welfare costs, but ecosystem-level benefits may support longer-term red squirrel population viability. Reintroduction programs must weigh these competing welfare dimensions carefully.