Pine martens have recovered naturally in Scotland and through reintroduction in Wales and England. Their return affects prey species welfare and ecosystem dynamics in complex ways.
Pine marten recovery creates a complex welfare picture. Grey squirrels caught by pine martens experience predation stress and death - from their perspective, a welfare negative. But the ecosystem effect - suppression of grey squirrels and recovery of red squirrels - represents a net welfare gain for native wildlife at the population level. Individual red squirrels that survive and breed because grey squirrel competition is reduced experience positive welfare outcomes they would not have had without pine marten presence. Predator-prey relationships involve individual suffering but are part of the natural welfare landscape that conservation seeks to restore.